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HUMAN PHYSIOLOGY. 

SEVENTH EDITION. ENLARGED. 


BRUBAKER. 



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4^1'hey are arranged in the most approved form, thorough and concise, containing 
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Visceral Anatomy. Can be used with either Morris’ or Gray’s Anatomy. 117 Illus¬ 
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No. 5. OBSTETRICS. Fifth Edition. By Henry G. Landis, m. d. Revised and 
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? QUIZ-COMPENDS ? No. 4. 


A 


COMPEND 


OF 


HUMAN PHYSIOLOGY. 


ESPECIALLY ADAPTED FOR THE USE OF 
MEDICAL STUDENTS. 


BY 


ALBERT P. BRUBAKER, A.M., M.D., 


DEMONSTRATOR OF PHYSIOLOGY IN THE JEFFERSON MEDICAL COLLEGE; PROFESSOR 
OF PHYSIOLOGY, PENNSYLVANIA COLLEGE OF DENTAL SURGERY; LECTUKBK 
ON ANATOMY AND PHYSIOLOGY, DREXEL INSTITUTE OF ART, 

SCIENCE, AND INDUSTRY; FELLOW OF THE COLLEGE 
OF PHYSICIANS OF PHILADELPHIA. 


SEVENTH EDITION, REVISED AND ENLARGED. 

WITH NEW ILLUSTRATIONS 


PHILADELPHIA: 

P. BLAKISTON, SON 


A TABLE OF PHYSIOLOGICAL CONST 


AND 



IOI2 WALNUT STREET. 

1893. 










Entered according to Act of Congress, in the year 1893, by 
P. BLAKISTON, SON & CO., 

In the office of the Librarian of Congress, at Washington, D. C. 


Press of Wm. F. Fell & Co., 
1220-24 Sansom St., 

PHILADELPHIA- 





PREFACE TO SEVENTH EDITION. 


In the preparation of a Seventh Edition of the Compend of Physiology, 
the attempt has again been made to still further adapt it to the necessities 
of medical students, during their attendance upon the lectures and in 
reviewing the subject prior to examinations. 

With these objects in view, not only has the book been revised, but 
special chapters on the Physiological Anatomy of the Skeleton and the 
Joints, the Physiology of Muscular Tissue and of special muscular groups, 
have been inserted. 

It is believed also, that these additional chapters will increase its useful¬ 
ness as a text-book for the study of physiology in those Normal and High 
Schools where it has already been in use. 

Notwithstanding the many additions which have been made in this and 
previous editions, care has been taken to keep the Compend what it was 
originally intended to be, viz : A compact and convenient arrangement of 
the fundamental facts of human physiology. 

Again, my thanks are due to all those teachers who have kindly noticed 
and recommended the Compend to their students. That it may continue 
to merit the approval of both teachers and students, is my earnest wish. 

ALBERT P. BRUBAKER. 


v 





TABLE OF CONTENTS 


PAGE 

Introduction,. 9 

The Skeleton, . n 

Structure and Mechanism of Joints,. 19 

Physiology of the Tissues,. 24 

Chemical Composition of the Body,. 31 

Food,. 57 

Digestion,. 62 

Absorption, .. 76 

Blood,. S3 

Circulation of Blood,. 89 

Respiration,. 98 

Animal Heat,.105 

Secretion,.108 

Mammary Glands,.111 

Vascular or Ductless Glands,.113 

Excretion,.114 

Kidneys,.114 

Liver,.122 

Skin,.127 

Nervous System,.130 

Properties and Functions of Nerves,.133 

Cranial Nerves,. 138 

Spinal Cord,. 153 

Spinal Nerves,.155 

Medulla Oblongata,.164 

vii 




























TABLE OF CONTENTS. 


viii 

PAGE 

Pons Varolii,.*68 

Crura Cerebri,.. • *68 

Corpora Quadrigemina,.169 

Corpora Striata and Optic Thalami,. .170 

Cerebellum,.* 7 * 

Cerebrum. 173 

Sympathetic Nervous System,.184 

Sense of Touch,.188 

Sense of Taste,.189 

Sense of Smell,.19 1 

Sense of Sight,. 19 1 

Sense of Hearing,.202 

Voice and Speech,.210 

Reproduction,.213 

Generative Organs of the Female,.213 

Generative Organs of the Male,. 216 

Development of Accessory Structures,.217 

Development of the Embryo,.222 

Table of Physiological Constants,.228 

Table Showing Relation of Weights and Measures of the 
Metric System to Approximate Weights and Measures 

of the U. S.,.231 

Index,.233 























COMPEND 

OF 

HUMAN PHYSIOLOGY. 


INTRODUCTION. 

Definitions.—If the body of any animal be dissected, it will be found 
to be composed of organs, such as the heart, stomach, lungs, brain, etc.; 
these organs again, upon a closer examination, will be found to be com¬ 
posed of simpler structures, known as tissues ; e. g., epithelial, connective, 
muscular, and nervous. A description of the several organs which make 
up the body of any animal, their external form, their internal arrangement, 
their relations to each other, constitutes the science of Animal Anatomy. 
This may naturally be divided into— 

1. Comparative Anatomy , the object of which is a comparison of the 
structures of two or more animals, with a view of determining their 
points of resemblance or dissimilarity. 

2. Special Anatomy , the object of which is the investigation of the 
construction, form, and arrangement of the organs and tissues of any 
individual animal. The study of the tissues, their properties, and 
minute structure constitutes that branch of anatomy known as His¬ 
tology. 

Human Anatomy is that department of anatomical science which has 
for its object the investigation of the construction of the human body. 

Animal Physiology is a study of the vital phenomena exhibited by the 
organs and tissues of which the body of any animal is composed. This 
may be divided into— 

I. Comparative Physiology , the province of which is a comparison of 
the vital phenomena exhibited by the various structures of two or more 
B 9 



10 


HUMAN PHYSIOLOGY. 


animals, for the purpose of unfolding their points of resemblance and 
dissimilarity. 

2. Special Physiology , the object of which is a study of the vital phe¬ 
nomena exhibited by any individual animal. 

Human Physiology is that department of physiological science which 
has for its object the study of the vital phenomena, functions, or actions 
exhibited by the organs and tissues of the human body in a state of health. 

The functions of the human body may be arranged in three groups 
viz.:— 

1. Nutritive Functions , which have for their object the preservation of 
the individual, e.g. } digestion, absorption, the formation and circulation 
of blood, respiration, calorification, secretion and excretion. 

2. Animal Functions , which bring the individual into conscious relation¬ 
ship with the external world, e.g., sensation, motion, language, 
mental and moral manifestations. 

3. Reproductive Functions which have for their object the preservation 
of the species. 

General Structure of the Animal Body.—The body of every 
animal, from fish to man, may be divided into 1, an axial, and 2, an 
appendicular portion. The axial portion consists of the head, neck, and 
trunk; the appendicular, of the anterior and posterior extremities, or 
limbs. 

The axial portion of all mammals, to which class man zoologically 
belongs, as well as all birds, reptiles, batrachians, and fish, has a hard, 
bony, segmented axis, running from before backward, known as the back 
bone or vertebral column, in virtue of which all the classes just mentioned 
form one great division of the animal kingdom, the Vertebrata . This 
axis, at its anterior extremity, is variously modified and expanded to form 
the head. In all vertebrate animals the vertebral column forms a partition 
between two cavities, viz., the dorsal and the ventral. The dorsal cavity, 
formed by the arching of bony processes arising from the bodies of the 
vertebra, is narrow but elongated; anteriorly it is expanded, and forms the 
cavity of the head. It contains the brain and spinal cord. The ventral 
cavity is confined mainly to the trunk, and contains the alimentary or food 
canal and its appendages, as well as the heart and larger blood-vessels. 
The alimentary canal begins on the ventral side of the head, at the mouth, 
and terminates at the posterior extremity of the body. 

In all mammals, the ventral cavity is subdivided by a transverse musculo- 
membranous partition into two smaller cavities, the thorax and abdomen. 


THE SKELETON. 


11 


The former contains the heart, lungs, and the anterior part of the alimentary 
canal, the gullet or esophagus; the latter contains the continuation of the 
alimentary canal, the stomach and intestines, and the organs in connection 
with it, the liver and pancreas. In the posterior portion of the abdominal 
cavity are placed the kidneys and organs of reproduction. The external 
surface of the entire body is covered over with the skin. The alimentary 
canal and the various cavities in connection with it are lined by a mucous 
membrane. Between the skin and mucous membrane are found bones, 
enveloped by muscles, blood-vessels, nerves, and lymphatics. The appen¬ 
dicular portions of the body contain no organs essential to life. They also 
consist fundamentally of bones, muscles, blood-vessels, nerves, and lym¬ 
phatics, covered with skin. The limbs are modified in form, and adapted 
for prehension and locomotion in accordance with the needs of the animal. 
The animal body is not, therefore, a homogeneous organism, but is com¬ 
posed of a number of diverse parts. These structures, which have certain 
peculiarities of structure in common, form anatomical systems; e.g ., the 
osseous or bony, the muscular, the nervous systems. A combination of 
several different structures working together for the accomplishment of a 
definite object constitutes a physiological apparatus; e.g., the digestive,the 
respiratory, and the urinary apparatus. As all vertebrate animals have the 
same fundamental plan of structure, and as their organs and tissues perform 
actions which closely resemble those of man, a general knowledge of the 
form, the construction, and the arrangement of the organs and tissues of 
different types of animal life forms an indispensable basis for the study of 
human physiology. 


THE SKELETON. 

Within the body of man and all vertebrated animals there is a highly 
developed framework, consisting of bones and cartilages, technically 
known as the skeleton (Fig. i), the function of which is to afford support 
to all the softer tissues, to afford attachment for muscles, and to protect 
many delicate organs from injury. In addition to the bony skeleton there 
is a secondary framework, composed for the most part of fibrous or con¬ 
nective tissue, which ramifies everywhere throughout the body, uniting its 
various parts and affording support and protection to the ultimate elements 
of the tissues. 

The skeleton naturally divides itself in accordance with the funda¬ 
mental division of the body into, I, an axial, and 2 , an appendicular 
portion. The axial portion consists of the bones of the spine, the head, 


Fig. i. 



12 
































THE SKELETON. 


13 


the ribs and sternum; the appendicular portion consists of the bones of 
the extremities and the bony arches by which they are united to the 
trunk. 

The Axial Skeleton.—The axial skeleton consists primarily of the 
spinal column, placed in the middle of the back of the neck and trunk, 
where it forms the foundation of the entire skeleton. It is composed of 
a series of superimposed bones termed vertebra; above it supports the 
skull; laterally it affords attachment for the ribs, which in turn support 
the weight of the upper extremities; below it rests upon the pelvic bones, 
which transmit the weight of the body to the inferior extremities. 

The Vertebral or Spinal Column consists in the child of 33 dis¬ 
tinct bones, which are arranged in groups, named and numbered from their 
position, as follows: Cervical, 7; thoracic, 12; lumbar, 5; sacral, 5 ; 
coccygeal, 4, the latter being quite rudimentary. In the adult the sacral 
and coccygeal bones unite to form two separate composite bones, the sac¬ 
rum and coccyx. Owing to their mobility the former are termed true, the 
latter false vertebrae. While the vertebrae of each group have certain char¬ 
acteristics in common, the type is best shown by the thoracic vertebrae. 

The Thoracic Vertebrae present the following parts: 1. A body or 
centrum , a short cylinder of bone slightly concave on its upper and lower 
surfaces, which is united to adjoining vertebrae by elastic discs of fibro-carti- 
lage. 2. A neural arch consisting of two symmetrical halves each arising 
from the back of the body and uniting in the median line. Each arch 
consists anteriorly of the pedicle, posteriorly of the lamina . At the point of 
union of the arches there is presented a prominent spine of bone which 
collectively give to the column its spiny character. From each side of 
the arch arises the transverse process, which projects outward and slightly 
backward. From the superior and inferior border of each lamina project 
the superior and inferior articulating processes. 

The Cervical Vertebrae differ in some respects from the thoracic. The 
body is smaller, the neural arch larger, the spinous process shorter and 
often bifid. The transverse processes are broader and perforated by a fora¬ 
men. The first and second vertebrae deviate markedly from the usual 
type. The first vertebra or atlas possesses neither a body nor a spinous 
process. It is practically a large neural ring provided with two lateral 
masses of bone which support the weight of the head. The second ve'rte- 
bra, or axis , has projecting from its body a vertical process, the odontoid 
process, around which the atlas bone rotates. 

The Lumbar Vertebrae are the largest in the spinal column. The cen- 


14 


HUMAN PHYSIOLOGY. 


trum gradually increases in width and strength from above downward, in 
accordance with the increasing weight of the body. The arches and pro¬ 
cesses are correspondingly enlarged. 

The Sacrum is a triangular-shaped bone placed below the vertebrae. Its 
anterior surface is concave and presents four transverse ridges which mark 
the points of union of the primitive vertebrae and four openings on either 
side which communicate with the neural canal. The posterior surface is 
convex and marked by numerous partially developed processes which are 
homologous with the processes of the upper vertebrae. 

The Coccyx is a rudimentary bone formed by the fusion of the bodies 
of four undeveloped vertebrae and terminates the spinal column. 

The Spinal Column as a whole has an average length of about twenty- 
eight inches. Viewed laterally, it presents from above downward four curves. 
In the cervical and lumbar regions the curves are convex anteriorly, in the 
thoracic and sacral regions concave. These curves, taken in connection 
with the elastic intervertebral disks, impart to the spinal column considerable 
elasticity. 

The Sternum is a thin, flat bone, situated in the median line in the 
anterior wall of the thorax. It consists of three segments, a superior, a 
middle, and an inferior, known respectively as the manubrium, the gladio¬ 
lus, and the xiphoid appendix. The lateral borders of the sternum present 
a series of depressions for the reception of the collar bone and the sternal 
ends of the cartilages of the first seven ribs. 

The Ribs form a series of narrow, curved, flattened bones, attached pos¬ 
teriorly to the dorsal vertebrae, and continued anteriorly to the median line 
by the intermediation of cartilage. There are 24 ribs in number, 12 on 
each side. The first 7 are termed true ribs, from their attachment to the 
sternum; the remaining 5 are termed false ribs, of which the cartilages of 
the eighth, ninth, and tenth are attached to each other, while the eleventh 
and twelfth are free or floating. The ribs increase in length from the first 
to the seventh, and then decrease to the twelfth. Each rib consists of a 
beveled head for articulation with the dorsal vertebrae, a constricted portion, 
the neck, a tubercle for articulation with the transverse process, a curved 
shaft, compressed from side to side. Collectively the ribs form the lateral 
walls of the chest. The costal cartilages are the continuations of the ribs, 
and serve to connect them to the sternum. 

The Thorax, as a whole, is a conical-shaped structure formed by the 
union of the thoracic vertebrae, the ribs, and sternum. It is compressed 


THE APPENDICULAR SKELETON. 


15 


from before backward, so that the antero posterior diameter is less than the 
transverse. The superior opening is oval in outline, measuring five inches 
from side to side, and two and one-half from before backward. The inferior 
opening is irregular, owing to the inclination of the ribs and the projection 
of the lower end of the sternum. 

The Skull consists of 22 bones, of which 8 form the cranium, which 
encloses and protects the brain; the remaining 14 support the face and 
form the orbital, nasal, and mouth cavities. The cranial-bones are : 1. 
The frontal bone , which forms the forehead and roof of the orbits. 2. A 
pair of parietal bones , which form the sides and roof of the cranium. 3. 
The occipital bone , which forms the back of the head and part of the base. 
It is perforated by a large opening, the foramen magnum; through which 
the spinal cord passes. On either side of the foramen there is a large con¬ 
dyle, which articulates with the lateral masses of the atlas. 4. A pair of 
temporal bones, which aid in forming the sides and base of the skull and 
lodge the auditory organ. 5. The sphenoid bone, an irregular-shaped bone, 
situated at the base of the skull, where it forms a keystone for the cranial 
arch. 6. The ethmoid bone, situated between the skull and nasal cham¬ 
bers, and giving support to the olfactory organs. 

The facial bones are paired, two only being single. The paired bones are : 
1. The superior maxillce, or upper jawbones, situated one on either side of 
the middle line, assisting in the formation of the orbit, nose, and roof of 
the mouth. They also carry the upper teeth. 2. The palatal bones com¬ 
plete the hard palate and assist in forming the posterior nares. 3. The 
* nasal bones forming the bridge of the nose. 4. The lachrymal bones, lying 
between the orbit and nose. 5. The malar bones , lying beneath and to the 
outside of the orbit. 6. The inferior turbinated bones, one in each nasal 
chamber. 7. The inferior maxilla, or lower jawbone, is connected with 
the temporal bone on each side of the head. It carries the lower teeth 
and assists in mastication. 8. The vomer forms a portion of the partition 
of the nose. 


THE APPENDICULAR SKELETON. 

The appendicular skeleton consists of: 1. The bones of the shoulder 
girdle and the bones of the arm, forearm, and hand. 2. The bones of 
the pelvic girdle, the bones of the thigh, leg, and foot. 

The Shoulder Girdle is an imperfect bony arch connecting the limb 
directly with the axial skeleton. It consists of two bones, the clavicle 
and scapula. 


16 


HUMAN PHYSIOLOGY. 


The clavicle is a cylindrical bone extending from the upper end of the 
sternum upward and outward to be attached to the acromion process of 
the scapula. 

The scapula is a flat triangular bone situated on the upper and back 
part of the thorax. It is not directly connected with the axial skeleton, 
being separated from it by a layer of muscle in which it is partly embedded. 
The posterior surface is divided by a spine of bone into two unequal 
portions. This spine gradually becomes more prominent as it passes from 
within outward ; toward its termination it curves forward and forms the 
acromion process with which the clavicle articulates. The upper part of 
the outer edge of the scapula presents a slightly concave surface, pyriform 
in shape, which receives the upper extremity of the arm bone, known as 
the glenoid fossa. Overhanging this fossa is a strong bony process— 
the coracoid. 

The skeleton of the arm and hand consists of 30 bones, the largest of 
which, the humerus, lies in the arm. The ulna and radius are placed side 
by side in the forearm, and are so arranged that the radius can move to 
some extent around the ulna. The wrist or carpus contains 8 small bones, 
the nietacarpus contains 5 long, cylindrical bones, and the fingers 3, and 
the thumb 2. 

The Pelvic Girdle, which forms the bond of union between the leg and 
the axial skeleton, consists of a single bone, the os innominatum , on each 
side, which articulates with the sacrum posteriorly; arching forward, it 
meets with its fellow of the opposite side in the median line, thus forming 
the lateral and anterior walls of the pelvic cavity. In the young child, this 
bone consists of 3 distinct bones, the ilium, ischium, and pubis, which, in 
adult life, fuse together to form the single bone. At the point of union on 
the external surface there is formed a large cavity, the acetabulum , which 
lodges the head of the thigh bone. 

The skeleton of the leg and foot consists of 30 bones. The thigh bone, 
or femur , is the largest bone in the body, extending from the pelvic girdle 
to the knee. It is provided above with a rounded head, which fits into the 
acetabulum. This is connected with the shaft by a short neck, which forms 
with the latter an angle of 125 0 . The lower extremity of the femur is en¬ 
larged to rest upon the bones of the leg. The leg bones are 2 in number, 
the tibia and fibula, the latter being placed external. In front of the knee 
is the patella. The tarsus consists of 7 bones, one of which, the astragalus, 
is united to the tibia and fibula to form the ankle. The calcaneum forms 
the heel. The metatarsus consists of 5 bones, each carrying a toe. There 
are 14 bones in the toes, 3 in each, except the large toe, which has but 2. 


STRUCTURE OF BONE. 


17 


Structure of Bone.—Osseous tissue, as distinguished from bone in the 
anatomical sense, belongs to the connective-tissue group (page 29), in 
which the fundamental substance is permeated with insoluble lime salts, 
the phosphate and carbonate being the most abundant. With dilute solu¬ 
tions of hydrochloric acid, these can be converted into soluble salts and 
dissolved out. The osseous matrix left behind is soft and •pliable, and yields 
gelatin on boiling. The surfaces of all bones in the recent state, except 
where they are covered with cartilage, are invested with a fibrous mem¬ 
brane, the periosteum. The inner surface of this membrane is loose in 
texture, and supports a fine capillary plexus of blood-vessels and numerous 
protoplasmic cells, the “ osteoblasts.” As this layer is directly concerned 
in the formation of bone, it is spoken of as the osteogenetic layer. 

A section of any bone shows that it is composed of two kinds of tissue, 
compact and cancellated. The compact resembles ivory, and is found on 
the outer surface ; the cancellated is spongy, and to the naked eye appears 
to be made up of thin, bony plates, which intersect each other in all direc¬ 
tions. It is found in great abundance in the interior of bones. The shaft 
of a long bone is hollow, the cavity extending almost from one extremity to 
the other. This central cavity, as well as the interstices of the cancellated 
tissue, is filled in the recent state with marrow. The marrow or medulla 
is a vascular tissue, the capillaries of which are supported by a delicate 
connective-tissue framework. In its meshes are to be found characteristic 
marrow cells, or osteoblasts, engaged in the formation of bone. The 
marrow in long bones is yellow, from the presence of fat resulting from a 
transformation of the protoplasm of connective-tissue cells. In the cancel¬ 
lated tissue, especially near the extremities, this fatty transformation does 
not take place, and the marrow remains red. The cells are supposed to 
give birth to red corpuscles. 

Examined microscopically, a thin, transverse section of a bone reveals 
numerous small oval or round openings, which are the transverse sections 
of canals which run, for the most part, in a longitudinal direction. These 
are the Haversian canals. In the living state, they are partly filled with 
blood-vessels and lymphatics. The canals are connected with each other 
and with the surfaces of the bones by numerous anastomosing branches. 
Around each Haversian canal is a series of concentric lamina, composed of 
fibers. Between every two laminae are found small cavities (lacunae) from 
which radiate in all directions small canals (canaliculi), which commu¬ 
nicate freely with each other. The Haversian canals, with their associated 
lacunae and canaliculi, form a series of intercommunicating passages, through 
which lymph passes for the nourishment of bone. In the cancellated 
tissue the blood-vessels pass through its interstices, and are supported by 


18 


HUMAN PHYSIOLOGY. 


connective tissue. Bone cells , protoplasmic and nucleated, are found in 
each lacuna. When young, they are branched, sending their prolongations 
into the canaliculi. 

Cartilage is a modified form of connective tissue. It is opaque, bluish- 
white in color, though in thin sections translucent. In some situations it 
is firm in consistence, in others soft and elastic. All cartilage consists 
primarily of a ground or fundamental substance throughout which are 
scattered cells. There are two principal varieties in the human body, viz : 
hyaline and fibro-cartilage. 

Hyaline cartilage is the most typical form, the matrix of which being 
translucent and homogeneous. It is found on the ends of bones entering 
into the formation of joints, where it forms articular cartilage, between the 
ribs and sternum, forming the costal cartilages. It is also found in other 
situations. 

Microscopically examined, the ground substance reveals the presence of 
oval or spherical corpuscles containing one or more nuclei. The cell sub¬ 
stance is frequently marked off from the ground substance by concentric lines, 
or fibers, which form a capsule for the cell. Repeated division of the cell 
substance frequently takes place, until the whole capsule is fully occupied 
with cells. The cell protoplasm is granular, and frequently contains drops 
of fat. According to some investigators the cell spaces are not isolated, 
but connected by fine channels, which in turn communicate with lymphatics. 
By these means nutritive fluid permeates the entire structure. 

Fibro-cartilage consists of two varieties, white and yellow. 

White fibro-cartilage consists of the usual ground substance pervaded 
by white fibers. It is firm and resistant, and found wherever strength 
and fixedness are required. Hence it is present between the vertebrae, 
forming the intervertebral discs, between the condyle of the lower jaw and 
glenoid fossa, in the knee joint, around the margins of cup-shaped cavities, 
etc. In these situations it assists in maintaining the apposition of the 
bones, in giving a certain degree of motility to joints, and in diminishing 
the effect of shock and pressure. The fibers of white cartilage are 
arranged in bundles and layers, the ground substances being relatively less 
abundant. Between the layers are the usual cartilage corpuscles. 

Yellow fibro-cartilage is found in the epiglottis, the external ear, Eus¬ 
tachian tube, and larynx. Primarily hyaline in character, the ground sub¬ 
stance becomes pervaded with yellow fibers which branch and interlace in 
all directions, forming a dense network, but are so arranged as to form small 
spaces in which are found cartilage corpuscles surrounded by a soft matrix. 
These fibers are very elastic, and give to this form of cartilage a con¬ 
siderable degree of elasticity. 


STRUCTURE AND MECHANISM OF JOINTS. 


19 


STRUCTURE AND MECHANISM OF JOINTS. 

The various bones comprising the skeleton do not form a rigid framework, 
but are united by a variety of structures and in such a manner as to admit 
of varying degrees of movement. The points of union are termed articu¬ 
lations,, or joints. 

The structures entering into the formation of joints are : I. Bones y the 
articulating surfaces of which are often expanded and variously modified, 
as in the case of long bones. 2. Hyaline cartilage , which covers the articu¬ 
lating surfaces. Owing to its smoothness it facilitates the gliding movements 
of opposed surfaces and by its elasticity diminishes the force of jars and 
shocks imparted to the bones. White fibro-cartilage in the form of inter- 
articular discs is found in many joints. Placed between the ends of bones 
it subdivides the articulation and adjusts dissimilar surfaces. 3. A synovial 
membrane , consisting of connective tissue mixed with elastic tissue. Its 
inner surface is lined with endothelium, which secretes the synovial fluid, a 
colorless, viscid alkaline fluid containing much mucin, albumin, and fat. Its 
function is to lubricate the articular surfaces and diminish friction. 4. 
Ligaments , tough bands of white fibrous tissue which pass from bone to 
bone in various directions. White fibrous tissue, being inextensible but 
pliant, maintains the bones in apposition and prevents displacement, but 
permits of easy movement within certain limits. 

Modes of Articulation.—All articulations are divided, according to 
the extent of movement, into— 

1. Synarthrodial , comprising those joints endowed with little or no 
motion; e. g ., joints or sutures uniting the bones of the skull. 

2. Amphiarthrodial , comprising those joints endowed with a slight degree 
of mobility in consequence of an intervening plate of fibro-cartilage and 
tough, unyielding ligaments; e.g. y vertebral and pelvic joints. 

3. Diarthrodial, comprising those joints which are freely movable, the 
extent of movement, however, being variable. In all such joints the articu¬ 
lating surfaces are generally adapted to each other, are covered with smooth 
cartilage, lubricated with synovial fluid, and surrounded by ligaments which, 
while not preventing, yet limit the extent of movement. The diarthrodial 
joints may be divided according to the character of the movement into (a) 
arthrodial, or gliding joints, ( b) ginglymus, or hinge joints, ( c ) enarthrodial, 
or ball and socket joints, ( d) trachoidal, or rotatory joints. 

The articulations may also be grouped in accordance with the funda¬ 
mental divisions of the skeleton into (1) axial, (2) appendicular. 


20 


HUMAN PHYSIOLOGY. 


THE AXIAL ARTICULATIONS. 

The axial articulations are quite numerous and may be grouped into those 
uniting : i. The bodies of the vertebrae, the intervertebral joints. 2. The 
vertebra with the ribs, the costo-vertebral joints. 3. The ribs with the 
sternum, the costo-sternal joints. 4. The vertebral column with the head, 
the occipito-atlantal joints. 

The Intervertebral Joints are amphiarthrodial in character. The 
bodies of the vertebrae are united by tough, elastic discs of fibro-cartilage 
which collectively constitute about one-quarter of the length of the vertebral 
column. The vertebrae are bound together by ligamentous bands situated 
on the anterior and posterior surfaces of their bodies and by short elastic 
bands between the neural arches and processes. These structures combine 
to render the vertebral column elastic and flexible, and to enable it to 
resist and diminish the force of shocks communicated to it. 

The function of the intervertebral joints and associated structures is not 
only to impart to the vertebral column the physical properties just men¬ 
tioned, but to endow it with certain forms of movement necessary to the 
performance of various bodily activities. While the extent of movement 
between any two vertebrae is slight, the sum total of movement of all the 
vertebrae is considerable. Again, the extent of movement varies in different 
regions of the column, being limited and dependent upon the character of 
the vertebrae, and the inclination of their articular processes. In the cervi¬ 
cal and lumbar regions the movements of extension and flexion are freely 
allowed, extension being greater in the former, flexion being greater in the 
latter, particularly between the fourth and fifth vertebrae. Lateral flexion 
takes place in all portions of the column, but is particularly marked in the 
cervical region. A rotatory movement of the column as a whole takes place 
through an angle of 28 degrees. This is most marked in the lower cervical 
and dorsal regions. In the dorsal region the surfaces of the articular pro¬ 
cesses lie in the arc of a circle, the center of which is in front of the 
vertebrae, and in consequence permit of considerable rotation. In the lum¬ 
bar region the reverse condition obtains and rotation is almost impossible. 

The Costo-vertebral and Costo-sternal joints are diarthrodial in 
character. The former are formed by the apposition of the heads of the ribs 
with the dorsal vertebrae and the rib tubercles with the transverse processes, 
the latter by the anterior extremities of the ribs and sternum through the 
intermediation of the costal cartilages. Both sets of joints are provided 
with ligaments and closed synovial sacs. 


THE APPENDICULAR ARTICULATIONS. 


21 


The function of the costo-vertebral joints is to permit of an elevation 
and depression of the ribs coincident with a forward and backward gliding 
movement, which is essential to changes in the diameters of the thoracic 
cavity during respiration. At the costo-sternal joints the movements are 
complex, the resultant, however, being an elevation of the anterior 
extremities of the ribs and an advance of the sternum during in¬ 
spiration. During expiration the reverse takes place. The resultant of a 
combination of all the movements permitted at these joints is an ele¬ 
vation of the thorax, an advance of the sternum, and in consequence an 
increase in the transverse and antero-posterior diameters during an in¬ 
spiratory movement. The reverse of these movements takes place during an 
expiratory movement. 

The Occipito-atlantal joints are formed by the apposition of the 
superior concave surfaces of the lateral masses of the atlas and the convex 
surfaces of the occipital condyles. 

The Atlanto-axoidean joints are formed laterally by the articular 
processes, centrally by the odontoid process, the anterior arch of the atlas, 
and the transverse ligament. 

The function of these joints is to give to the head great variety and * 
range in its movements. In flexion and extension the movement takes 
place around a transverse axis, the occipital condyles gliding alternately 
backward and forward upon the lateral masses of the atlas. The rotation of 
the head is accomplished by a movement of the collar formed by the atlas 
and the transverse ligament around the odontoid process of the axis, which 
is so extensive as to permit of a range of vision through 18o°. 


THE APPENDICULAR ARTICULATIONS. 

The appendicular articulations comprise all those entering into the for¬ 
mation of— 

1. The shoulder girdle, arm, and hand. 

2. The pelvic girdle, leg, and foot. 

The Shoulder Girdle presents two articulations. The sterno-clavic- 
u/ar, which unites the clavicle to the sternum, and the acrontio-clavicular. 

The function of these joints is to endow the shoulder girdle with 
considerable mobility—enabling it to execute a series of movements upon 
the thorax. 

The Shoulder Joint, formed by the union of the hemispherical head 
of the humerus and the glenoid fossa of the scapula, belongs to the 


22 


HUMAN PHYSIOLOGY. 


enarthrodial, or ball and socket, variety. Though surrounded by ligaments 
and a synovial membrane, the bones are retained in position largely by at¬ 
mospheric pressure and muscular action. 

The function of this joint is to endow the arm with great freedom 
of movement. Being a typical enarthrodial joint the movements can take 
place in all directions; and consist of flexion; extension; abduction, 
which, at an angle of 90°, is checked by the locking of the great 
tuberosity of the humerus with the acromion process of the scapula; ad¬ 
duction ; circumduction, in which the arm describes a cone the apex of 
which is in the joint, the base at the distal extremity; rotation, in which 
the humerus revolves outward or inward around a vertical axis drawn 
through its head. 

The Elbow Joint is formed by the union of the lower end of the 
humerus with the sigmoid cavity of the ulna and the cup-shaped de¬ 
pression on the head of the radius. Owing to the configuration of these 
bones, great security is afforded this joint, independent of its ligamentous 
attachment. 

The function of this joint is to permit movements of flexion and 
' extension only, the former being limited at an angle of 30 to 40° by 
the contact of the coronoid process with the humerus, the latter by the 
contact of the olecranon process with the humerus, when the ulna is in a 
straight line. This joint is not, strictly speaking, a true ginglymus joint, 
inasmuch as flexion and extension are attended by a screw-like move¬ 
ment as the ulna glides over the obliquely disposed articular surface of 
the humerus. 

The Superior Radio-ulnar joint is formed by the lesser sigmoid cav¬ 
ity of the ulna and the vertical border of the head of the radius, the latter 
being held firmly in position by the orbicular ligament. 

The Inferior Radio-ulnar joint is formed by the concavity on the 
inner aspect of the radius and the inferior extremity of the ulna. 

The function of these joints is to permit movements of pronation and 
supination of the hand. The disposition of the ligaments at both articula¬ 
tions allows the head of the radius to revolve around a vertical axis and 
the inferior extremity to revolve around the ulna. In both supination and 
pronation the radius carries the hand with it. 

The Radio-carpal, or wrist joint, is formed by the union of the inferior 
quadrilateral surface of the radius, the triangular fibro-cartilage and convex 
surfaces of the carpal bones, the scaphoid, semilunar, and cuneiform. 


THE APPENDICULAR ARTICULATIONS. 


23 


The Carpal, Metacarpal, and Phalangeal joints are formed by the 
union of the bones entering into the formation of the skeleton of the 
hand. 

The function of these joints is to endow the hand with all varieties 
and combinations of movements, enabling it to perform a large number of 
delicate and complicated actions. 

The Pelvic Girdle presents anteriorly the inter-pubic joint and poste¬ 
riorly the sacro-iliac joints. 

The function of these joints, which are amphiarthrodial in character, 
is not so much to permit of movement, which is slight, as to prevent the 
forward and downward displacement of the sacrum and to enable it to 
transmit the weight of the body through the pelvic girdle to the lower ex¬ 
tremities. 

The Hip Joint is formed by the acetabulum on the outer surface of the 
os innominatum and the globular head of the femur, both structures being 
accurately adapted to each other. To retain the femur in position the acetabu¬ 
lum is deepened by a rim of cartilage ; to render the joint more stable and 
to limit the extent of motion it is provided with strong ligaments and 
strengthened by overlying muscles. 

The function of the hip joint is to permit all those movements of the 
trunk on the femur, or the reverse, which are involved in walking, running, 
rowing, and allied muscular acts. Being atypical enarthrodial joint, move¬ 
ments can take place in all directions within certain limits, and may be grouped 
as follows: I. A pendulum-like movement in any plane. 2. Rotation 
around the long axis of the limb. 3. Circumduction* in which the limb de¬ 
scribes a cone, the apex of which is in the joint, the sides being formed by 
the limb itself. 

The Knee Joint is formed by the apposition of the articular surfaces of 
the femur, tibia, and patella. It is partially subdivided by the interposition of 
two fibro-cartilages. From the mechanical construction of this articulation 
displacement of the bones would readily take place were it not provided, 
as it is, with a large number of ligaments, tendons, and synovial membranes, 
which are so arranged as to make it the most complicated joint in the 
body. 

The function of the knee joint, being ginglymus in structure, is to per¬ 
mit movements of flexion and extension, which cover an angle of about 
145°. These simple movements, however, are complicated by a gliding of 
the condyles upon the tibial facets so that the points of contact are con- 


24 


HUMAN PHYSIOLOGY. 


stantly shifting. Owing to the shape of the condyles, extension is accom¬ 
panied by outward rotation and flexion by inward rotation. 

The Ankle Joint unites the skeleton of the foot to the lower extremity 
of the leg, and is formed by the apposition of the convex surface of the 
astragalus and the concavity of the tibia, and embraced on either side by the 
external and internal malleoli. 

The function of the ankle joint is to permit of flexion and extension 
around an axis passing through the body of the astragalus, but at such an angle 
that the movements do not take place in a direct antero-posterior plane, but 
in a plane directed outward and forward. It serves to transmit the weight 
of the body to the foot. 

The Tarsal, Metatarsal, and Phalangeal joints unite the bones of 
the foot. They are very numerous and abundantly supplied with liga¬ 
ments and synovial membranes. 

The function of these joints is to endow the arches of the foot with 
considerable elasticity, to diminish the effects of jars or shocks that are 
transmitted to the vertebral column, and to adapt the foot to changes of form 
necessitated by the acts of walking, jumping, etc. 


PHYSIOLOGY OF THE TISSUES. 

The study of the Structure of the body reveals that it is composed 
of a number of dissimilar parts, such as the brain, heart, lungs, muscles, etc., 
to which the name organ has been given. The organs upon_a closer exam¬ 
ination can be resolved into elementary structures, to which the name tissue 
has been given. The study of the physical and physiological properties of 
the tissues has given rise to that department of anatomy known as histology, 
or, as it is largely prosecuted with the microscope, microscopical anatomy. 
Notwithstanding the complexity of the body, the number of constituent 
tissues is not great. They can be classified as follows :— 

1. Epithelial. 

2. Connective , comprising the areolar, adipose, fibrous, elastic, cartilage 
and bone. 

3. Muscular. 

4. Nervous. 

The majority of the tissues, however, are not simple structures, but com¬ 
plexly organized masses, whose physiological properties are dependent upon 


PHYSIOLOGY OF THE TISSUES. 


25 


and the resultant of the properties of the structural elements composing 
them. 

Cells.—When the tissues are subjected to microscopical analysis, it is 
found that instead of being homogeneous they are complex structures com¬ 
posed of simpler elements to which the name cell has been given. The 
cell constitutes the primary, elementary, structural, or form element, of all 
tissues, and may be said to consist of a minute mass of living matter. 
Every organized body takes its origin in a single cell, the ovum. However 
complex its structures may become, it can be shown by an ultimate analysis 
that they are composed of similar cells or of fibers, which are the products 
or modifications of cells. The cell may be defined, therefore, as the prim¬ 
ary morphological and physiological unit of the organic world, to which 
every exhibition of life, whether normal or abnormal, is to be referred. 

Structure of Cells.—Cells vary in their anatomical constitution in the 
different structures of the body and may be classed in three groups, viz. :— 

1. Cells consisting of a cell substance, a nucleus, and one or more nu 
cleoli , enclosed within a cell membrane, all these parts being found in the 
primitive ovum. 

2. Cells consisting of a cell substance and a nucleus only; most of the 
cells of animal tissues have this structure. To this type of cell the name 
cytode has been given. 

3. Cells consisting of the cell substance only. 

Cells vary in size within considerable limits, from the size of a w'hite 
blood cell, syg^th of an inch, to that of the multipolar cells in the anterior 
horns of the gray matter of the spinal cord, atjo^ °f an i nc ^> or to that of 
the ovum, the jl^th of an inch. They also differ considerably in shape, 
according to the locality in which they are found. When young and free 
to move in a fluid medium, they assume the spherical form ; when subjected 
to pressure, they may assume cylindrical, polygonal, fusiform, and stellate 
forms. 

The Cell Substance consists of a soft, transparent, gelatinous, semi¬ 
fluid material, known as protoplasm or bioplasm. Though frequently 
homogeneous, it often exhibits a finely granular appearance. The charac¬ 
teristics of protoplasm, however, vary in different tissues and in different 
animals. While young cells consist almost entirely of protoplasm, mature 
cells contain, in addition, materials of an entirely different kind; e. g ., 
globules of fat, granules of glycogen, mucigen, pigment, digestive ferments, 
as pepsin, trypsin, etc., substances which are produced by the physiological 
action of the protoplasm, 
c 


26 


HUMAN PHYSIOLOGY. 


The chemical composition of living protoplasm is difficult of determina¬ 
tion. When dead, it is found to be composed of water, proteid material, 
a small quantity of glycogen, fat, and inorganic salts. 

When examined with the microscope, the cell substance or protoplasm 
exhibits a network, the spongioplasm , in the meshes of which is contained a 
transparent material, the kpa/op/asm. The protoplasm of all cells possesses, 
in a varying degree, the property of irritability; that is, of reacting in a 
definite manner to some form of excitation. The response will vary accord¬ 
ing to the character of the element stimulated. If it be a muscular fiber, 
there will result a contraction ; if it be a gland cell, a secretion. In some 
animal cells, as well as in many vegetable cells, currents are visible in the 
protoplasmic mass, which, in the absence of apparent external influences, are 
said to be spontaneous. Ameboid movements are observed in many animal 
cells, particularly when young. The irritability and other physiological 
properties of protoplasm are dependent upon a due supply of nourishment 
and the maintenance of a normal temperature. 

The Nucleus is an ovoid or spherical body embedded in the cell sub¬ 
stance. It consists of a distinct membrane, enclosing a clear nuclear sub¬ 
stance, which, however, is pervaded by an irregular network of fibers, which 
exhibit here and there enlargements, to which the term nucleoli is given. 
The meshes of this network contain a soft, interstitial substance. The 
nuclear membrane and the fibers composing the network, staining readily 
with various dyes, are spoken of as chromatin ; the interstitial substance, 
not staining, as achromatin. 

The Cell Membrane is a very thin, transparent, homogeneous, and 
elastic structure, completely enclosing the cell substance. It varies in 
thickness and consistency in different tissues. It is permeable to water and 
aqueous solutions of various organic and inorganic substances. The cell 
membrane has no special physiological activity, merely serving as a pro¬ 
tective agent. It is a product of the cell substance. 


MANIFESTATIONS OF CELL LIFE. 

Growth and Assimilation.—All cells exhibit the three fundamental 
properties of life: growth, motion, and reproduction. Every living cell is, 
therefore, the seat of a series of chemical changes underlying the two 
phases of nutrition, assimilation and disassimilation. By the first process, 
the cell absorbs from its surroundings those materials necessary for its 
growth and physiological activities. When newly reproduced, all cells are 


MANIFESTATIONS OF CELL LIFE. 


27 


exceedingly small, but by the absorption of nutritive material and its subse¬ 
quent assimilation and vitalization they gradually attain their mature size. 
Some of the absorbed material, instead of becoming an integral part of the 
protoplasm, is oxidized, giving rise to heat and force. As a result of cellu¬ 
lar activity, there is also formed within the cell special substances, which, 
being finally eliminated, play some important part in nutrition. Coincident 
with the assimilative process, there are changes taking place of a disassimi- 
lative character; absorbed material, as well as tissue itself, is constantly 
being reduced to simpler forms, as carbon dioxid, urea, water, etc. The 
nutrition of the cell is, therefore, an epitome of the nutrition of the body as 
a whole. 

Reproduction.—Like all organic structures cells have a limited period 
of life ; their continual decay and death necessitates a capability of repro¬ 
duction. Cells reproduce themselves in the higher animals mainly by 
fission. This is seen in the white blood corpuscles of the young embryos 
of animals; the corpuscle here consists of a cell substance and nucleus. 
When division of the cell is about to take place, the nucleus elongates, the 
cell substance assumes the oval form, a constriction occurs, which gradually 
deepens, until the original cell is completely divided and two new cells are 
formed, each of which soon grows to the size of the parent cell. 

In cells provided with a cell membrane the process is somewhat differ¬ 
ent. In the ova of the inferior animal, after fertilization has taken place, 
a furrow appears on the opposite sides of the cell substance, which deepens 
until the cell is divided into two equal halves, each containing a nucleus; 
this process is again repeated until there are four cells, then eight, and so 
on until the entire cell substance is divided into a mulberry mass of cells, 
completely occupying the interior of the cell membrane. The whole pro¬ 
cess of segmentation takes place with great rapidity, occupying not more 
than a few minutes, in all probability. 

Motion.—In addition to the currents frequently observed in cell proto¬ 
plasm, various other forms of movement have been observed: ameboid 
movements, the projection of pseudopodia, the waving of cilia, the activity 
of spermatozooids, the migration of blood-corpuscles, are among the different 
types of movement exhibited by many of the cells of the body. 

By a combination of these primary structural elements, and of fibers and 
ground substances derived from or specially produced by them, all the 
tissues are formed which enter into the construction of the different organs 
of the body. 


28 


HUMAN PHYSIOLOGY. 


CLASSIFICATION AND PROPERTIES OF THE 
TISSUES. 

Epithelial Tissue.—The epithelial tissue consists of one or more 
layers of cells resting upon a homogeneous membrane, the other side of 
which is abundantly supplied with blood-vessels. The form of the epithe¬ 
lial cell, varying in different situations, may be flattened, spheroid, or col¬ 
umnar, and is related to some special function. When arranged in layers, 
the cells are united by an intercellular substance. The epithelial tissue 
forms a continuous covering for the surfaces of the body. The external 
investment, the skin, as well as the mucous membrane which lines the 
entire alimentary canal and its associated body cavities, is formed in all 
situations by the basement membrane, covered with one or more layers of 
cells. All materials, therefore, whether nutritive or excretory, must pass 
through epithelial cells before they can enter into the formation of tissues 
or be eliminated from them. Chemically, epithelial cells are composed 
largely of keratin, a small proportion of water, and inorganic salts. 

The consistency of epithelium varies in accordance with external influ¬ 
ences, such as want of moisture, pressure, friction, etc. This is well seen 
in the skin and palms of the hands and soles of the feet, where it acquires 
its greatest density. In the intestines, lungs, and other cavities, where the 
reverse conditions prevail, the epithelium is extremely soft. The epithelial 
tissues possess varying degrees of cohesion and elasticity, which enable them 
to resist considerable pressure and distention without having their integrity 
destroyed. Being bad conductors of heat, they assist in preventing rapid 
radiation from the body, and so maintain the normal temperature. The 
physiological activity of all epithelial tissue depends upon a due supply of 
nutritive material furnished by the blood, which not only maintains its own 
nutrition, but affords material from which are formed the secretions of 
glands, whether of the skin or mucous membranes. 

The functions of the epithelial tissues are : i. To serve as a protec¬ 
tive covering to the underlying structures. Wherever there is repeated 
pressure, the epithelial cells become thick and indurated. Owing to their 
consistence they resist to some extent the injurious influences of acids and 
alkalies and various poisons. 2. As an absorbing agent. Inasmuch as 
the skin and mucous membrane cover the surfaces of the body it is obvious 
that all nutritive substances entering the body must first traverse the epithe¬ 
lium. The epithelial cells covering the skin, owing to their density, play 
but a feeble role in man. The mucous membrane of the alimentary canal 
is the principal absorbing surface. The character of its epithelium permits 


CLASSIFICATION AND PROPERTIES OF TISSUES. 


29 


of the absorption of water, peptones, sugars, salts. The epithelium lining 
the pulmonary air vesicles is actively engaged in taking up oxygen and 
giving out carbon-dioxid. 3. As an eliminating agent. Waste products, 
however produced within the organism, must be taken up by the epithelium 
of the various excretory organs before being finally disposed of. The secre¬ 
tions of all glands are products of epithelial activity. 

Connective Tissue.—The bony skeleton of the body is supplemented 
by a finer skeleton, composed of connective tissue, which pervades the entire 
body, and which, under various forms, serves as a bond of connection be¬ 
tween its different parts, as a covering and protection for various organs, 
and as a basis of support for the elements of muscular, nervous, and gland¬ 
ular tissues. 

The connective tissues include several varieties, among which may be 
mentioned areolar, adipose, fibrous, elastic, cartilaginous, and osseous. 
Notwithstanding their apparent diversity, they have many points of similarity. 
They have a common origin, developing from the same embryonic material; 
they have much the same structure, passing imperceptibly into each other, 
and functionally perform the same office, viz., supporting and connecting 
the specific elements of the tissues or organs. 

Areolar Tissue .—This variety is found widely distributed throughout 
the body in all situations. It serves to unite the skin and mucous mem¬ 
branes to the structures on which they rest, to unite and support blood¬ 
vessels, muscles, nerves, etc. When examined with the naked eye it 
presents the appearance of fine, transparent, colorless fibers, of delicate 
membranous lamina, which cross each other in every direction, leaving 
spaces or areolae between them. Examined microscopically, these fibers 
are found to be composed of still finer white fibers cemented together by a 
transparent substance containing mucin. Other fibers are distinguishable 
by their straight course, their dark outline, their tendency to branch and to 
unite with adjoining fibers. When torn across they curl up at their extremi¬ 
ties, owing to their property of elasticity. Distributed throughout the 
meshes of the areolar tissue are found flattened, irregularly branched or 
stellate corpuscles, the connective tissue corpuscles, plasma cells, and 
granule cells. 

Adipose Tissue .—This exists very generally throughout the body, but is 
found most abundantly beneath the skin, around the kidneys, and in the 
bones. It is composed almost entirely of small vesicles more or less 
completely filled with fat globules. The wall of the vesicle is protoplasmic, 
and contains at some points an oval flattened nucleus. Adipose tissue can 
arise wherever connective tissue is found. It would appear that the gran- 


30 


HUMAN PHYSIOLOGY. 


ules of fat are produced by a transformation of the albuminous contents ot 
the connective-tissue corpuscles. The vesicles are grouped together to 
form lobules, which in turn form irregular masses supported by connective 
tissue and blood-vessels. 

Retiform Tissue. —This is also a variety of connective tissue made up 
very largely of white fibers interlacing in all directions. The spaces or 
areolae are wanting in the usual ground substance, but are filled with fluid. 
Connective-tissue corpuscles are abundant, but elastic fibers are absent. 
Adenoid tissue is but ordinary retiform tissue, the spaces of which, however, 
are filled with lymph corpuscles. It is found in lymphatic glands, in the 
central nervous system, and other situations. 

Fibrous Tissue. —White fibrous tissue is exceedingly abundant and 
important. It forms the ligaments which hold the bones together, the 
tendons of the muscles, the membranes covering bones, cartilages, the septa 
of muscles, etc. Fibrous tissue is tough and strong but wholly inextensible 
and, in consequence, is admirably adapted to fulfil various mechanical 
functions in the body. It is quite pliant,bending readily in any direction, but 
difficult to break. When examined microscopically it is found to be com¬ 
posed of white fibers, resembling in all respects those of areolar tissue. 
Treated with acetic acid they swell up and become indistinct. When boiled 
they yield gelatin, a derivative of collagen. 

Elastic Tissue. —The elastic tissue is also an important member of the 
connective-tissue group. It is almost invariably associated with white 
fibers in some proportion, but in some tissues, as the ligamentum nuchae, 
the ligamenta subflava, the coats of the large Slood-vessels, it exists almost 
alone. In its pure state it presents a distinctly yellow appearance. The 
fibers of which it is composed are transparent, but present a distinct outline; 
they run almost parallel, but give off branches which unite to form a reti¬ 
culated structure. As the name implies, these fibers are very extensible 
and elastic. Cartilage and bone have been considered in connection with 
the skeleton. 

Physical and Physiological Properties of Connective Tissue.— 
Among the physical properties may be mentioned consistency, which varies 
from the semi-liquid to the solid state. This variation depends upon the 
quantity of water in the individual tissues. Their cohesion, with the excep¬ 
tion of the softer varieties, is considerable, and offers great resistance to 
traction, pressure, torsion, etc. In the various movements of the body, in 
the contraction of muscles, in supporting weights, in diminishing the effects 
of shocks, the properties of consistence and cohesion play important parts. 
Wherever the various forms of connective tissue are found, their chemical 


CHEMICAL COMPOSITION OF THE HUMAN BODY. 


31 


composition and structure are found to be in relation to their mechanical 
function. If traction be the preponderating force, the structures become 
fibrous, as in ligaments and tendons, and the cohesion greatest in the longi¬ 
tudinal direction. If pressure be exerted in all directions, as upon mem¬ 
branes, the fibers become interlaced and so offer an uniform resistance. 
When pressure is exerted in a definite direction, as upon the ends of long 
bones, the tissue assumes the cartilaginous form. Elasticity is also a pro¬ 
perty of all connective tissues, but is most marked in those containing an 
abundance of yellow elastic fibers. Elasticity plays an important role in 
many physiological acts. It not only opposes and limits forces of traction, 
pressure, torsion, etc., but upon their cessation returns the tissues or struc¬ 
tures to their original condition. It thus maintains the natural form and 
position of the organs by counterbalancing and opposing temporarily acting 
forces. 


CHEMICAL COMPOSITION OF THE HUMAN 

BODY. 

By chemical analysis the solids and fluids of the body can be first re¬ 
duced to a number of compound substances which are termed proximate 
principles; these again can be resolved by an ultimate analysis into fifteen 
chemical elements. The different chemical elements thus obtained, and 
the proportions in which they exist, are shown in the following table : — 


Oxygen, . 
Hydrogen, 
Nitrogen, . 
Carbon, 
Sulphur, . 

. 72.00 
9.10 
2.50 
. '13.50 
.147 

Phosphorus, 

1.15 

Calcium, . 

1.30 

Sodium, 

.10 

Potassium, 

.026 

Magnesium, 

.001 


O. H. and C. are found in all the tissues and 
fluids of the body, without exception. 

O. H. C. and N. found in most of the fluids 
and all tissues except fat. 

. . In fibrin, casein, albumin, gelatin; as potas¬ 
sium sulpho-cyanide in saliva; as alkaline 
sulphate in urine and sweat. 

. . In fibrin and albumin; in brain; as tri-sodium 
phosphate in blood and saliva, etc, 

. . As calcium phosphate in lymph, chyle, blood, 
saliva, bones, and teeth. 

. . As sodium chlorid in all fluids and solids of 
the body, except enamel; as sodium sulphate 
and phosphate in blood and muscles. 

. . As potassium chlorid in muscles; generally 
found with sodium as sulphates and phos¬ 
phates. 

. . Generally in association with calcium, as phos 
phate, in bones. 




HUMAN PHYSIOLOGY. 


32 

Chlorin, . . .085 

Fluorin, . . . .08 

Iron,.01 

Silicon, ... a trace 
Manganesium a trace 


. In combination with sodium, potassium, and 
other bases, in all the fluids and solids. 

. As calcium fluorid in bones, teeth, and urine. 

. In blood globules; as peroxid in muscles. 

. In blood, bones, and hair. 

. Probably in hair, bones, and nails. 


Of the four chief elements which together make up gy per cent, of the 
body, O. H. N. are eminently mobile, elastic, and possess great atomic heat. 
C. H. N. are distinguished for the narrow range and feebleness of their 
affinities and chemical inertia. C. has the greatest atomic cohesion. O. is 
noted for the number and intensity of its combinations, and its remarkable 
display of chemical activity. 

Chemical Elements, with the exception of the gases, O. H. and N.,do 
not exist alone in the body, but are combined in characteristic proportions 
to form compounds, the proximate principles, the ultimate compounds to 
which the fluids and solids can be reduced. 


Proximate Principles exist in the body under their own form, and can 
be extracted without losing their distinctive properties. 

There are about one hundred proximate principles, which are divided 
into four classes, viz. : inorganic , organic non-nitrogenized, organic nitro- 
genized, and principles of waste. 


I. INORGANIC PROXIMATE PRINCIPLES. 


SUBSTANCE. 

Oxygen,. 

Hydrogen, ...... 

Nitrogen,.. 

Carbonic anhydrid, . . . 
Carburetted hydrogen, 1 
Sulphuretted hydrogen, ( 

Water,. 

Sodium chlorid, . . . . 
Potassium chlorid, . . . 
Ammonium chlorid, . 
Calcium chlorid, . . . . 
Calcium carbonate, . . . 
Calcium phosphate, ] 
Magnesium phosphate, | 
Sodium phosphate, 
Potassium phosphate, J 
Sodium sulphate, ) 
Potassium sulphate, j 
Sodium carbonate, ) 
Potassium carbonate, / 
Magnesium carbonate, . 


WHERE FOUND. 

Lungs and blood. 

Stomach and intestines. 

Blood and intestines. 

Expired air of lungs. 

Lungs and intestines. 

Found in all solids and fluids. 

In all fluids and solids except enamel. 

In muscles, liver, saliva, gastric juice, etc. 
Gastric juice, saliva, tears, urine. 

Bones, teeth, urine. 

Bones, teeth, cartilage, internal ear, blood. 


In all fluids and solids of the body. 


Universal except milk, bile, and gastric juice. 

Bones, blood, lymph, urine, etc. 

Blood and sebaceous matter. 








CHEMICAL COMPOSITION OF THE HUMAN BODY. 


33 


Oxygen is one of the constituent elements of all the fluids and solids of 
the body. It is found in a free state in the respiratory passages and intesti¬ 
nal tract; it is held in solution in the lymph and plasma and forms a loose 
combination with the hemoglobin of the blood corpuscles. The function 
of the oxygen in the body appears to be the oxidation of albuminous, 
oleaginous, and saccharine compounds to their ultimate forms, urea, car¬ 
bonic acid, water, etc. As to whether this is brought about by direct oxi¬ 
dation or by a fermentative process is yet unknown. As oxygen only enters 
into combination under a high temperature, it is assumed that it exists in 
the body under the form of ozone, 0 3 , which possesses remarkably active 
oxidizing powers. The seat of oxidation is at present located in the tissues, 
as the presence of ozone in the blood has not been positively demonstrated. 

Hydrogen is also a constituent element of almost all the compounds of 
the body ; it exists in a free state in the intestinal tract, where it is produced 
by a decomposition of organic substances; it is also produced within the 
tissues as a result of chemical changes. Its function is unknown, though 
it is asserted by Hoppe-Seyler that hydrogen unites with neutral oxygen, 
0 2 , in the tissues, forming water and liberating oxygen in the nascent state, 
which becomes the oxidizing agent. The process is represented in the fol¬ 
lowing equation :— 

HH + 0 2 -f n = H 2 0 + On, 
in which n represents the oxidizable substance. 

Water is an essential constituent of all the tissues of the body, consti¬ 
tuting about 70 per cent, of the entire body weight. It is introduced into 
the body in the form of drink and as a constituent of all kinds of food. 
The average quantity consumed daily is about four pints. While in the 
body, water acts as a general solvent, gives pliability to various tissues, and 
promotes the passage of inorganic and organic matters through animal 
membranes. It also promotes chemical changes which are essential to 
absorption and assimilation of food and the elimination of products of 
waste. It is probable that water is also formed within the body by the 
union of oxygen with the surplus hydrogen of the food. It is eliminated 
by the skin, lungs, and kidneys. 

Sodium chlorid is present in all the solids and fluids of the body, with 
the exception of enamel. It regulates osmotic action, holds the albuminous 
principles of the blood in solution, and preserves the form and consistence 
of blood corpuscles and the cellular elements of the tissues, by regulating 
the amount of water entering into their composition. 

Calciujn phosphate is the most abundant of all the inorganic principles 
with the exception of water, and is present to a great extent in bone, teeth, 


34 


HUMAN PHYSIOLOGY. 


muscles, and milk. It gives the requisite consistency and solidity to the 
different tissues and organs. In the blood, it is held in solution by the 
albuminous constituents. 

The Sodium and Potassium phosphates are present in most of the solids 
and fluids, and give to them their alkaline reaction. They are chiefly de¬ 
rived from the food. 

II. ORGANIC NON-NITROGENIZED PRINCIPLES. 

The organic non-nitrogenized principles are derived mainly from the 
vegetable world, but are also produced within the animal body. They are 
divided into: ist, the carbohydrates, comprising starch and sugar, bodies 
in which the oxygen and hydrogen exist in the proportion to form water, 
the amount of carbon being variable ; 2d, the fats, bodies having the same 
elements entering into their composition, but with the carbon and hydrogen 
increased and the oxygen diminished in amount; 3d, fatty acids; 4th, alco¬ 
hols. 

sugars, c. h. o. 

Dextrose Group. Cane-sugar Group. 

Dextrose (Glucose, grape sugar). Saccharose (cane sugar). 

Levulose. Maltose. 

Galactose. Lactose. 

The members of the dextrose group have a composition as follows: 
C 6 Hi 2 0 6 , and are frequently spoken of as mono-saccharids. The members 
of the cane-sugar group have a composition as follows : C 12 H 22 O n , and are 
frequently spoken of as di-saccharids. 

Dextrose has been found in many of the tissues and fluids of the body 
as a normal constituent. As it is readily assimilable, it is probable that 
under this form the carbohydrates are absorbed into the blood. As its name 
implies, it rotates the plane of polarized light to the right. 

Levulose is found in the stomach and intestine, and occasionally in the 
urine. It is formed by a decomposition of saccharose. While resembling 
dextrose in many respects, it differs from it in rotating the plane of polarized 
light to the left. 

Galactose can be obtained from brain substance by the action of boiling 
sulphuric acid and by the decomposition of lactose. It is also dextro¬ 
rotatory. 

Saccharose is the form of sugar largely consumed as food. It is largely 
distributed throughout the vegetable kingdom in the juices of fruits and 
plants. It is not found, however, as a constituent of any of the fluids or 
solids of the body. During its passage through the stomach and intestine 
it is converted by the action of ferments into equal parts of dextrose and 


CHEMICAL COMPOSITION OF THE HUMAN BODY. 


35 


glucose by the assumption of a molecule of water. Cane sugar is, there¬ 
fore, not absorbed under its own form, as it is non-assimilable, appearing in 
the urine after its injection into the blood. 

Maltose is the final product formed by the action of saliva and pancre¬ 
atic juice on starch paste. It is also non-assimilable, and is, probably, con¬ 
verted into dextrose after or during absorption. 

Lactose is the form of sugar naturally present in milk. It resembles the 
two preceding founs in being non-assimilable and non-fermentable. 

Glycogen is the only form of starch found as a constituent of the animal 
tissues. It is closely related to the sugars. 

The sugar of the body is derived from the food. After being converted 
into dextrose in the alimentary canal, it is absorbed into the blood by the 
veins of the portal system, and for the most part stored up in the liver under 
the form of glycogen. When the tissues require sugar for the performance 
of their normal activities, it is returned to the circulation and carried to all 
portions of the body. Whatever the intermediate stages may be, sugar is 
ultimately oxidized, contributing to the production of heat. It is eliminated 
under the forms of C 0 2 and H 2 0 . 

NEUTRAL FATS. C. O. H. 

Palmitin. 

Stearin. 

Olein. 

The Neutral fats , when combined in proper proportions, constitute a 
large part of the fatty tissue of the body ; they are soluble in ether, chloro¬ 
form, and hot alcohol; insoluble in cold alcohol and water, and liquefy at 
a high temperature; when a neutral fat is subjected to a high temperature 
in the presence of water and an alkali, it is decomposed, with the assimi¬ 
lation of the elements of water, into a fatty acid and glycerin. The fatty 
acid combines with the alkali and forms an oleate, palmitate, or stearate, 
according to the fat used. A similar decomposition of the neutral fats is 
said to take place in the small intestine during digestion. When thoroughly 
mixed with pancreatic juice, the fats are reduced to a condition of emulsion , 
a state in which the fat is minutely subdivided and the small globules held 
in suspension. 

FATTY ACIDS. C. O. H. 

Palmitic acid. Propionic acid. 

Stearic acid. Butyric acid. 

Oleic acid. Caproic acid. 

The Fatty acids , combined with sodium, potassium, and calcium, are 


36 


HUMAN PHYSIOLOGY. 


found as salts in various fluids of the body, such as blood, chyle, feces, 
etc. Phosphorized fats in nervous tissue, butyric acid in milk, propionic 
acid in sweat, are also constituents of the body. 

The Fats are derived from the food, both animal and vegetable. They 
are deposited in the form of small globules in the cells of the different 
tissues, are suspended in various fluids, are deposited in masses in and 
around various anatomical structures and beneath the skin. Independent 
of the fat consumed as food, there is good experimental»evidence that fat 
is also produced within the animal body from a partial decomposition of 
the albuminous compounds. Fat serves as a non-conductor of heat, gives 
roundness and form to the body, and protects various structures from 
injury. The fats are ultimately oxidized, thus giving rise to heat and 
force, and are finally eliminated as carbonic acid and water. 

ALCOHOLS. 

Glycerin. Cholesterin. Alcohol 

Glycerin is chemically atriatomic alcohol in combination with the neutral 
fats of the body. During pancreatic digestion it is set free. It is supposed 
by many physiologists to be directly concerned in the production of glyco¬ 
gen. Cholesterin is a crystallizable substance largely present in the bile, 
though it is found in other fluids and solids. It is supposed to be a waste 
product of nervous matter. Alcohol has been found in the urine. It is 
supposed to be the result of an alcoholic fermentation in the intestine. 

III. ORGANIC NITROGENIZED PRINCIPLES. 

The nitrogenized orproteid compounds are organic in their origin, being 
derived from the animal and vegetable world ; they are taken into the body 
as food, appropriated by the tissues, and constitute their organic basis; they 
differ from the non-nitrogenized substances in not being crystalline, but 
amorphous, in having a more complex but just as definite composition, and 
containing, in addition to C. O. H., nitrogen, with, at times, sulphur and 
phosphorus. The proteids possess characteristics which distinguish them 
from all other substances: viz., a molecular mobility, which permits isomeric 
modifications to take place with great facility; a catalytic influence, in 
virtue of which they promote, under favorable conditions, chemical changes 
in other substances; e. g., during digestion, salivin and pepsin cause starch 
and albumin to be transformed into sugar and albuminose respectively. 
Different proteids possess varying proportions of water, which they lose 
when subjected to desiccation, becoming solid; but upon exposure to 


CHEMICAL COMPOSITION OF THE HUMAN BODY. 


37 


moisture they again absorb water, regaining their original condition—they 
are hygroscopic. Another property is that of coagulation, which takes 
place under certain conditions : e. g., the presence of mineral acids, heat, 
alcohol, etc. 

After death the nitrogenized compounds undergo putrefactive changes, 
give rise to carburetted and sulphuretted hydrogen and other gases. In 
order that these changes may take place it is essential that certain condi¬ 
tions be present: viz., atmospheric air or some fluid containing oxygen, 
moisture , and a temperature varying between 6o° and 90° F. The cause 
of the putrefactive change is the presence of a minute unicellular organism, 
the bacterium termo. 

The nitrogenized bodies found in the organism are quite numerous, and 
although they resemble each other in many particulars, there are yet im¬ 
portant differences; they can be arranged into the following groups:— 

1. Native Albumins. —Proteid bodies soluble in water, many acids, and 
usually in alkalies; coagulabl? at a temperature of from 140° to 163° F. 

a. Serum Albumin , the principal form of albumin found in the animal 
fluids and solids. 

b. Egg Albumin, not found in ordinary tissues, but present in white 
of egg. 

2. Globulins. —Proteid bodies insoluble in water, but soluble in solutions 
of sodium chlorid. 

a. Globulin, found in many tissues, but largely present in crystalline 
lens. 

b. Myosin, found in the muscles in life in a fluid condition; after 
death it undergoes coagulation, giving rise to the rigidity of the 
muscles. 

c. Paraglobulin, present in blood and obtained from it by passing 
a stream of carbon dioxid through it; it is also precipitated by add¬ 
ing sodium chlorid. 

d. Fibrinogen, present in serous fluid and blood, and can be precipi¬ 
tated by the prolonged use of carbon dioxid; it is also precipitated 
by the addition of 12 to 16 per cent, of sodium chlorid. 

3. Derived Albumins.— Proteid bodies which are not coagulable by heat ; 
insoluble in pure water and in salt solutions; soluble in both acid and 
alkaline solutions. 

a.. Acid Albumin, found principally in the stomach during first stage 
of digestion, the result of the action of the hydrochloric acid upon 
the albumin of the food. 


38 


HUMAN PHYSIOLOGY. 


b. Alkali Albumin, found in the intestine during pancreatic digestion, 
the result of the action of alkalies upon the albumin of the food. 

c. Casein, the chief proteid of milk; it is precipitated by acetic acid 
and rennet. 

4. Peptones. —These bodies are formed in the stomach and intestinal 
tract by the action of the gastric and pancreatic juices upon the albumins 
of the food. They are very soluble in water, alkaline and acid solutions; 
non-coagulable by heat; very diffusible. They are precipitated by tannic 
acid and alcohol. 

5. Albuminoids. —The albuminoids are the results of various modifica¬ 
tions of albumins occurring during the nutritive process, as well as by 
the action of various external influences. 

a. Mucin , the characteristic ingredient of mucus secreted by the 
mucous membranes, giving to it its viscidity. 

b. Chondrin, found in cartilage. 

c. Gelatin, found in connective tissue, tendons, ligaments, bones, etc. 

d. Elastin, found in elastic tissue. 

e. Keratin, found in skin and epidermic appendages, nails, hair, 
horn, etc. 

6. Fibrin. —A filamentous albumin obtained by washing blood clots. It 
is insoluble in water and mineral acids. 

As the properties of the compounds formed by the union of elements are 
the resultants of the properties of the elements themselves, it follows that 
the ternary substances, sugars, starches, and fats, possess a great inertia and 
a notable instability; while in the more complex albuminous compounds, 
in which sulphur and phosphorus are united to the four chief elements, 
molecular mobility, resulting in isomerism, exists in a high degree. As 
these compounds are unstable, of a greater molecular mobility, they are 
well fitted to take part in the composition of organic bodies, in which there 
is a continual movement of composition and decomposition. 

IV. PRINCIPLES OF WASTE. 

Urea, Xanthin, Sodium, 

Creatin, Tyrosin, Potassium, I it t 

Cteatinin, Hippuric Acid, Ammonium, ra es ' 

Cholesterin, Calcium Oxalate, Calcium, 

These principles, which represent waste, are of organic origin, arising 
within the body as products of disassimilation or retrograde metamorphosis 
of the tissues; they are absorbed by the blood, carried to the various 
excretory organs, and by them eliminated from the body. 

The excrementitious substances will be fully considered under excretion. 



GENERAL PHYSIOLOGY OF MUSCULAR TISSUE. 


39 


Proximate Quantity of the Chemical Elements and Proximate 


Principles of the Body, Weighing 154 lbs. 

lbs. yxst. lbs. oz. 

Oxygen,..m . . Water,..in . . 

Hydrogen,.14 . . Albuminoids,.23 7 

Nitrogen, ....... 3 8 Fats,.12 . . 

Carbon, . ..21 . . Calcium phosphate, . . 5 13 

Calcium,. 2 . . Calcium carbonate, . . 1 

Phosphorus,. 1 12 Calcium fluorid, ..... 3 

Sodium, etc.,.12 Sodium sulphate, etc., ... 9 


154 • • 154 • • 


GENERAL PHYSIOLOGY OF MUSCULAR 
TISSUE. 

The Muscular Tissue, which closely invests the bones of the body, 
and which is familiar to all as the flesh of animals, is the immediate cause of 
the active movements of the body. This tissue is grouped in masses of 
varying size and shape, which are technically known as muscles. Muscles 
are so arranged and connected, for the most part with the bones, in such a 
manner, that by an alteration in their form they can change not only the 
position of the bones with reference to one another, but can also change the 
individual’s relation to surrounding objects. They are, therefore, the active 
organs of both motion and locomotion, in contradistinction to the bones and 
joints, which are but passive agents in the performance of the corresponding 
•movements. In addition to the muscular masses which are attached to the 
skeleton, there are also other collections of muscular tissue surrounding 
cavities such as the stomach,intestine, blood-vessels, etc., which impart to 
their walls motility, and so influence the passage of material through them. 

Muscles produce movement of the structures to which they are attached 
by the property with which they are endowed, of changing their shape, 
shortening or contracting under the influence of a stimulus transmitted to 
them from the nervous system. Muscles are, therefore, divided into: 1. 
Voluntary muscles , comprising those whose activity is called forth by stim¬ 
uli of the nerves as the result of an act or effort of volition. 2. Involun¬ 
tary muscles , comprising those whose activity is entirely independent of the 
volition. The voluntary muscles are also known from their attachment to 
the skeleton as skeletal , and from their microscopic appearance as striped 
muscles. The involuntary muscles, from their relation to the viscera of the 













40 


HUMAN PHYSIOLOGY. 


body are known also as visceral , and from their microscopic appearance as 
plain or smooth muscles. 

General Structure of Muscles.—All skeletal muscles consist of a 
central fleshy portion, the body or belly, which is provided at either ex¬ 
tremity with a tendon in the form of a cord or membrane by which it is 
attached to the bones. The belly is the contractile region, the source of the 
motor activity; the tendon is an inactive region and merely transmits the 
movement to the bones. 

A skeletal muscle is a complex organ consisting of muscular fibers, con¬ 
nective tissue, blood-vessels, and lymphatics. The general body of the 
muscle is surrounded by a dense layer of connective tissue, the epimysium , 
which blends with and partly forms the tendon; from its inner surface 
septse of connective tissue pass inward and group the muscular fibers into 
larger and smaller bundles, termed fasciculi. The fasciculi invested by this 
special sheath, the perimysium, are irregular in shape, and vary considerably 
in size. The fibers of the fasciculi are separated from each other and sup¬ 
ported by a delicate connective tissue, the endomysiutn. The connective 
tissue thus surrounding and penetrating the muscle binds its fibers into a 
distinct organ, and affords support to blood-vessels, nerves, and lymphatics. 
The muscular fibers are arranged parallel to each other, and their direc¬ 
tion is that of the long axis of the muscle. In length they vary from 30 to 
40 millimeters, and in diameter from 20 to 30 micromillimeters. 

The Vascular Supply to the muscles is very great and the disposition 
of the capillary vessels with reference to the muscular fiber is very charac¬ 
teristic. The arterial vessels after entering the muscle are supported by the 
perimysium ; in this situation they give off short, transverse branches, which 
immediately break up into a capillary network of rectangular shape, within 
which the muscular fibers are contained. The muscular fiber in intimate 
relation with the capillary is bathed with lymph derived from it. Its con¬ 
tractile substance, however, is separated from the lymph by its own invest¬ 
ing membrane, through which all interchange of nutritive and waste mate¬ 
rials must take place. Lymphatics are present in muscle, but confined to the 
connective tissue, in the spaces of which they take their origin. 

The Nerves which carry the stimuli to a muscle enter near its geometric 
center. Many of the fibers pass directly to the muscular fibers with 
which they are connected; others are distributed to blood-vessels. Every 
muscular fiber is supplied with a special nerve fiber except in those instances 
where the nerve trunks entering a muscle do not contain as many fibers as 
the muscle. In such cases the nerve fibers divide until the number of 


GENERAL PHYSIOLOGY OF MUSCULAR TISSUE. 


41 


branches equals the number of muscular fibers. The individual muscle 
fiber is penetrated near its center by the nerve, the ends being practically 
free from nerve influence. The stimulus that comes to the muscle fiber 
acts primarily upon its center and then travels in both directions to the ends. 

Histology of the Muscular Fiber.—A muscular fiber consists of a 
transparent elastic membrane, the sarcolemma, enclosing the true muscular 
contents. Examined microscopically, the fiber presents a series of alternate 
dim and bright bands, giving to it a striated appearance. 

When the bright band is examined with high magnifying powers a fine 
dark line is seen crossing it transversely. It was supposed by Krause to 
be the optical expression of a membrane which divides the cavity of the 
sarcolemma into a series of compartments, each of which contains a dim 
band of sarcous or muscle substance bounded at either extremity with the 
half of a bright band. This membrane has since been resolved into a row 
of granules. 

The muscular fiber also exhibits a longitudinal striation indicating that it 
is composed of fibrillae, placed side by side and imbedded in some inter- 
fibrillar substance, to which the name sarcoplasm has been given. The 
fibrillae which are arranged longitudinally to the long axis of the fiber are 
grouped by the intervening material into bundles of varying size, the 
muscle columns. The fibrillae which extend throughout the length of the 
fiber are not of uniform thickness, but present at regular intervals well- 
marked constrictions. 

In the region of the dim band, the fibrilla presents itself in the form of 
a homogeneous prismatic rod, termed sarcostyle , separated from neighboring 
rods by a slight amount of sarcoplasm. Between two successive rods is 
found a dark granule united by a thin band of similar material to the ends 
of the rods. The transverse row of granules corresponds to Krause’s mem¬ 
brane. 

In the region of the granules there is a diminution of the sarcous sub¬ 
stance, but an increase in the amount of sarcoplasm, and as the latter is 
more transparent than the former, the fiber presents at this point a conspic¬ 
uous bright band. Rollet considers the sarcostyles to be pre-existent, not 
the result of post-mortem or chemical changes, and the seat of the contrac¬ 
tile elements. The sarcoplasm is a passive material similar in its properties 
to protoplasm. 

Briicke has shown that when the muscular fiber is examined under 
crossed Nichol prisms the dim band appears bright and the bright band 
appears dim against a dark background, indicating that the former is 
doubly refractile, or anisotropic, the latter singly refractile, or isotropic. 

D 


42 


HUMAN PHYSIOLOGY. 


The fiber, therefore, appears to be composed of alternate discs of anisotropic 
and isotropic substance. 

Structure of Non-striated Muscular Fiber.—As the name implies, 
the involuntary fiber is non-striated, being apparently uniform and homo¬ 
geneous in appearance. When isolated the fiber presents itself in the form 
of an elongated fusiform cell varying from the one-tenth to the one-six 
hundredth of an inch in length. In some animals the fiber exhibits a 
longitudinal striation, as if it were composed of fibers. The cell is sur¬ 
rounded by a thin, elastic membrane and contains a distinct oval nucleus. 
The fibers are usually arranged in bundles and lamellae and held together 
by a cement substance and connective tissue. This non-striated muscular 
tissue is found in the muscularis mucosae of the alimentary canal as well 
as in the muscular walls of the stomach and intestines, in the posterior part 
of the trachea, in the bronchial tubes, in the walls of the blood-vessels, 
and in many other situations. 

Chemical Composition of Muscle.—The chemical composition of 
muscle is imperfectly understood, owing to the fact that some of its constit¬ 
uents undergo a spontaneous coagulation after death and that the chemical 
methods employed also tend to alter its normal composition. When fresh 
muscle is freed from fat and connective tissue, frozen, rubbed up in a mor¬ 
tar, and expressed through linen, a slightly yellow, syrupy, alkaline or neu¬ 
tral fluid is obtained, known as muscle plasma. This fluid at normal 
temperature coagulates spontaneously and resembles in many respects the 
coagulation of blood plasma. The coagulum subsequently contracts and 
squeezes out an acid muscle serum. The coagulated mass is termed myosin. 
This proteid belongs to the class of globulins. Inasmuch as it is not 
present in living muscle and only makes its appearance in the as yet living 
muscle plasma, it is probable that it is derived from some pre-existing 
substance, which is supposed to be myosinogen. Myosin is digested by 
pepsin and trypsin. According to Halliburton,.muscle plasma contains the 
following proteid bodies: Myosinogen, paramyosinogen, albumin, myoalbu- 
mose, all of which differ in chemical composition and respond to various 
chemical and physical reagents. 

Ferment bodies, such as pepsin and diastase; non-nitrogenized bodies, 
such as glycogen, lactic, and sarco-lactic acid, fatty bodies, and inosite ; 
nitrogenized extractives, e. g., urea, uric acid, kreatinin, as well as inor¬ 
ganic salts, have been obtained from the muscle serum. 

Metabolism in Muscles.—The chemical changes which underlie the 
transformation of energy in living muscles are very active and complex. 


GENERAL PHYSIOLOGY OF MUSCULAR TISSUE. 


43 


As shown by an analysis of the blood flowing to and from the resting 
muscle, it has, while passing through the capillaries, lost oxygen and 
gained carbon dioxid. The amount of oxygen absorbed by the muscle, 
9 per cent., is greater than the amount of C 0 2 given off, 6.7 per cent. 
There is no parallelism between these two processes, as C 0 2 will be given 
off in the absence of oxygen, or in an atmosphere of nitrogen. 

In the active or contracting muscle both -the absorption of oxygen and 
the production of C 0 2 are largely increased, but the ratio existing between 
them differs considerably from that of the resting muscle, for the quantity 
of oxygen absorbed amounts to 12.26 per cent., the quantity of C 0 2 10.8 
per cent. (Ludwig). Moreover, in a tetanized muscle the quantity of 
C 0 2 given off may be largely in excess of the oxygen absorbed. From 
these facts it is evident that the energy of the contraction does not depend 
upon the direct oxidation of certain substances, but upon the decomposition 
of some unstable compound of high potential energy, rich in carbon and 
oxygen. When the muscle is active, its tissue changes from a neutral to an 
acid reaction from the development of sarcolactic, and possibly phosphoric 
acids. The amount of glycogen present in muscle, 0.43 per cent., 
diminishes, but muscles wanting in glycogen, nevertheless, retain their 
power of contraction. Water is absorbed. The amount of urea is not 
materially increased by muscular activity, unless it is excessive and pro¬ 
longed, and then only in the absence of a sufficient quantity of non-nitro- 
genized material. Coincident with muscular contraction, the blood-vessels 
become widely dilated, leading to a large increase in the blood supply and 
a rapid removal of products of decomposition. 

Rigor Mortis.—A short time after death the muscles pass into a con¬ 
dition of extreme rigidity or contraction, which lasts from one to five days. 
In this state they offer great resistance to extension, their tonicity disap¬ 
pears, their cohesion diminishes, their irritability ceases. The time of the 
appearance of this post-mortem or cadaveric rigidity varies from a quarter 
of an hour to seven hours. Its onset and duration are influenced by the 
condition of the muscular irritability at the time of death. When the irri¬ 
tability is impaired from any cause, such as disease or defective blood sup¬ 
ply, the rigidity appears promptly, but is of short duration. After death 
from acute diseases it is apt to be delayed, but to continue for a longer 
period. 

The rigidity appears first in the muscles of the lower jaw and neck ; 
next in the muscles of the abdomen and upper extremities, finally in the 
trunk and lower extremities. It disappears in practically the same order. 

Chemical changes of a marked character accompany this rigidity. The 


44 


HUMAN PHYSIOLOGY. 


muscle becomes acid in reaction from the development of sarcolactic acid, 
it gives off a large quantity of carbonic acid, is shortened and diminished 
in volume. 

The immediate cause of the rigidity appears to be a coagulation of the 
myosinogen within the sarcolemma, with the subsequent formation of 
myosin and muscle serum. In the early stages of coagulation restitution 
is possible by the circulation of arterial blood through the vessels. The 
final disappearance of this contraction is due to the action of acids dis 
solving the myosin, and possibly to putrefactive changes. 

Source of Muscular Energy.—According to most experimenters, it 
is certain that normal muscular activity is not dependent on the metabolism 
of nitrogenous materials, inasmuch as its chief end product, urea, is not 
increased. The marked production of C 0 2 points to the combustion oi 
some non-nitrogenous matter; e. g ., glycogen, especially as this substance 
disappears during muscular activity. Muscles wanting in glycogen are, 
nevertheless, capable of contracting for some time. Moreover, there is no 
proof of the direct combustion of glycogen or any other carbohydrate. It 
has been suggested by Hermann that the energy of a muscular contraction 
may be due to the splitting and subsequent re-formation of a complex body 
belonging neither to the carbohydrates or fats, but to the albumins. To 
this body the term inogen has been given. This complex molecule, the 
product of the metabolic activity of the muscle cell, in undergoing decompo¬ 
sition would yield C 0 2 , sarcolactic acid, and a proteid residue resembling 
myosin. With the cessation of the contraction, the muscle protoplasm 
recombines the proteid residue with oxygen, carbohydrates, and fats, and 
again forms inogen. 

The phenomena of rigor mortis support such a view. At the moment of 
this contraction the muscle gives off C 0 2 in large amounts, the muscle 
becomes acid, and myosin is formed. There is thus a close analogy 
between the two processes; in other words, a contraction is a partial death 
of the muscle. As to what becomes of the myosin formed during a con- 
traction, nothing is known. It may be used in the formation of new 
inogen. 

The Physical Properties of Muscular Tissue.—The consistency oi 
muscular tissue varies considerably, according to the different states of the 
muscle. In a state of tension, it is hard and resistant; when free from 
tension, it is soft and fluctuating, whether the muscle is contracting or rest¬ 
ing. Tension alone produces hardness. The cohesion of muscular tissue 
is less than that of connective tissue, and is broken more readily. Cohesion 
resists traction and pressure, and lasts as long as irritability remains. 


GENERAL PHYSIOLOGY OF MUSCULAR TISSUE. 


45 


The elasticity of a muscle, though not great, is almost perfect. After 
being extended by a weight, it returns to its natural form. The limit of 
elasticity, however, is soon passed. A weight of 50 or 100 grams will 
overcome the elasticity so that it will not return to its original length. In 
inorganic bodies the extension is directly proportional to the extending 
weight, and the line of extension is straight. With muscles the extension 
is not proportional to the weight. While at first it is marked, the elonga¬ 
tion diminishes as the weight increases by equal increments, so that the 
line of extension becomes a curve. In other words, the elasticity of a 
passive muscle increases with increased extension. On the contrary, the 
elasticity of an active is less than a passive muscle, for it is elongated more 
by the same weight, as shown by experiment. 

Tonicity is a property of all muscles in the body, in consequence of 
being normally stretched to a slight extent beyond their natural length. 
This may be due to the action of antagonistic muscles or to the elasticity 
of the parts of the skeleton to which they are attached. This is shown by 
the shortening of the muscle which takes place when it is divided. Muscu¬ 
lar tonus plays an important rdle in muscular contraction. Being always 
on the stretch, the muscle loses no time in acquiring that degree of tension 
necessary to its immediate action on the bones. Again, the working power 
of a muscle is increased by the presence of some resistance to the act of 
contraction. According to Marey, the amount of work is considerably 
increased when the muscular energy is transmitted by an elastic body to the 
mass to be moved, while, at the same time, the shock of the contraction is 
lessened. The position of a passive limb is the resultant also of the elastic 
tension of antagonistic groups of muscles. 

Muscular Excitability or Contractility are terms employed to denote 
that property of muscular tissue in virtue of which it contracts or shortens 
in response to various excitants or stimuli. Though usually associated with 
the activity of the nervous system, it is nevertheless an independent endow¬ 
ment and persists after all nervous connections are destroyed. If the nerve 
terminals be destroyed, as they can be by the introduction of curara into 
the system, the muscles become completely relaxed and quiescent. The 
strongest stimuli applied to the nerves fail to produce a contraction. Various 
external stimuli applied directly to the muscle substance produces at once 
the characteristic contraction. The excitability of muscle is therefore an 
inherent property, dependent on its nutrition and persisting as long as it 
is supplied with proper nutritive materials and surrounded by those external 
conditions which maintain its chemical or physical integrity. 


46 


HUMAN PHYSIOLOGY. 


Muscular Contractions.—All muscular contractions occurring in the 
body under normal physiological conditions are either voluntary , caused 
by a volitional effort and the transmission of a nerve impulse from the 
brain through the spinal cord and nerves to the muscles; or reflex, caused 
by a peripheral stimulation and the transmission of a nerve impulse to the 
spinal cord, to be reflected outward through the same nerves to the muscles. 
In either case the resulting contraction is essentially the same. The normal 
or physiological stimulus which provokes the muscular contraction is a 
nerve impulse the nature of which is unknown, but is perhaps allied to a 
molecular disturbance. After removal from the body muscles remain in a 
state of rest, inasmuch as they possess no spontaneity of action. Though 
consisting of a highly irritable tissue, they cannot pass from the passive to 
the active state except upon the application of some form of stimulation. 

The stimuli which are capable of calling forth a contraction may be 
divided into : I, mechanical; 2, chemical; 3, physical. 

Every mechanical stimulus of a muscle, e.g., pick, cut, or tap, providing 
it has sufficient intensity and is repeated with sufficient rapidiiy, will cause 
not only a single but a series of contractions. 

All chemical agents which impair the chemical composition of the muscle 
with sufficient rapidity, e.g., hydrochloric acid, acetic and oxalic acids, dis¬ 
tilled water injected in the vessels, etc., act as stimuli, and produce single 
and multiple contractions. Physical agents, as heat and electricity, also 
act as stimuli. A muscle heated rapidly to 30° C. contracts vigorously, 
and reaches its maximum at 45 0 C. Of all forms of stimuli the electrical 
is the most generally used. Two forms are used—the induced current and 
the make-and-break of a constant current. 

Changes in a Muscle During Contraction.—When a muscle is 
stimulated either indirectly through the nerve, or directly by any external 
agent, it undergoes a series of changes which relate to its form, volume, 
optical, physical, chemical, and electrical properties. These changes in 
their totality constitute the muscular contraction. 

1. Form .—The most obvious’change is that of form. The fibers become 
shorter in their longitudinal and wider in their transverse diameters, and 
the muscle as a whole becomes shorter and thicker. The degree of short¬ 
ening may amount to 30 per cent, of the original.length. 

2. Volume .—The increase in transverse diameter does not fully compen¬ 
sate for the diminution in length, for there is at the moment of contraction 
a slight shrinkage in volume which has been attributed to a compression 
of air in its interstices. 

3. Optical Changes .—If a muscular fiber be examined microscopically 


GENERAL PHYSIOLOGY OF MUSCULAR TISSUE. 


47 


during its contraction, it will be observed that when the contraction wave 
begins both bright and dim bands diminish in height and become broader, 
though this change is more noticeable in the region of the bright band. 
This Englemann attributes to a passage of fluid material from the bright 
into the dim band. At the time of relaxation there is a return of this ma¬ 
terial and the fiber assumes its original shape and volume. As the con¬ 
traction wave reaches its maximum, the optical properties of both the 
isotropic and anisotropic bands change. The former , which was originally 
clear, now becomes darker and less transparent, until at the crest of the 
wave it assumes the appearance of a distinct dark band. The latter , the 
anisotropic, which was originally dim, now becomes, in comparison, clear 
and light. This change in optical appearance is due to an increase in 
refrangibility of the isotropic and a decrease in the anisotropic bands coin¬ 
cident with the passage of fluid from the former into the latter. There is 
at the height of the contraction a complete reversal in the positions of the 
striations. At a certain stage between the beginning and the crest of the 
wave there is an intermediate point at which the strise almost entirely dis¬ 
appear, giving to the fiber an appearance of homogeneity. There is, how¬ 
ever, no change in refractive power as shown by the polarizing apparatus. 
After the contraction wave has reached the stage of greatest intensity, there 
is a reversal of the above phenomena, and the fiber returns to its original 
condition, which is one of relaxation. 

Physical Changes .—The extensibility of muscle is increased during the 
contraction, the same weight elongating the fibers to a greater extent than 
during rest. The elasticity, or its power of returning to its original form, 
is correspondingly diminished. 

Chemical Changes .—The metabolism of muscle during the contraction 
is very active. There is an increase in the production of carbon dioxid 
and the absorption of oxygen. The muscle changes from an alkaline or 
neutral to an acid reaction, from the development of sarcolactic acid. The 
muscle also become warmer. The electrical changes will be treated of 
in connection with nerves. 

Transmission of the Contraction Wave.—Normally when a mus¬ 
cle is stimulated by the nerve impulse the shortening and thickening of the 
fibers begin at the end organ and travel in opposite directions to the ends 
of the muscle. This change propagates itself in a wave-like manner and 
has been termed the contraction wave. If a stimulus be applied directly 
to the end of a long muscle, the contraction wave passes along its entire 
length to the opposite extremity in virtue of the conductivity of muscular 
tissue. The rapidity of the propagation varies in different animals—in 


48 


HUMAN PHYSIOLOGY. 


the frog from 3 to 4 meters per second, in man from 10 to 13 meters. The 
length of the wave varies from 200 to 400 millimeters. 

Graphic Record of a Muscular Contraction.—The changes in the 
form of a muscle during contraction and relaxation have been carefully 
studied by recording the muscular movement by means of an attached 
lever, the end of which is applied against a traveling surface. The time 
relations of all phases of the muscular movement are obtained by placing 
beneath the lever a pen attached to an electro-magnet thrown into action by 
a tuning fork vibrating in hundredths of a second. A marking lever records 
simultaneously the moment of stimulation. 

Single Contraction.— When a single electrical induction shock is 
applied to a nerve close to the muscle, the latter undergoes a quick pulsa¬ 
tion, speedily returning to its former condition. As shown by the muscle 

Fig. 2. 


* 


MUSCLE CURVE PRODUCED BY A SINGLE INDUCTION SHOCK APPLIED TO A MUSCLE. 

a-f. Abscissa, a-c. Ordinate, a-b. Period of latent stimulation, b-d. Period of in¬ 
creasing energy, d-e. Period of decreasing energy, e-f. Elastic after vibrations. (Lan~ 
dois .) 

curve (see Fig. 2), there is between the moment of stimulation and the 
beginning of the contraction a short but measurable period, known as the 
latent period, during which certain chemical changes are taking place pre¬ 
paratory to the exhibition of the muscular movement. Even when the 
electrical stimulus is applied directly to the muscle a latent period, though 
shorter, is observable. The duration of this period in the skeletal muscles 
of the frog has been estimated at 0.01 of a second, but it has been shown by 
the employment of more accurate methods and the elimination of various 
external influences to be much less, not more than 0.0033 to 0.0025 of a 
second. 

The contraction follows the latent period. This begins slowly, rapidly 
reaches its maximum, and ceases. This has been termed the stage of rising 
or increasing energy. The time occupied in the stage of shortening is 
about 0.04 second, though this will depend on the strength of the stimulus, 





GENERAL PHYSIOLOGY OF MUSCULAR TISSUE. 


49 


the load with which the muscle is weighted, and the condition of the mus¬ 
cular irritability. 

The relaxation immediately follows the contraction. This takes place 
at first slowly, after which it rapidly returns to its original length. This is 
the period of falling or decreasing energy and occupies about 0.05 second. 
The whole duration of a muscular contraction occupies, therefore, about 
0.1 second. 

Residual , or after vibrations, are frequently seen which are due to changes 
in the elasticity of the muscle. The amplitude of the contraction depends 
upon the condition of the muscle, the load, the strength of stimulus, etc. 

Contraction of Non-striated Muscle.—The curve obtained by regis¬ 
tration of the contraction of non-striated muscle shows that it is similar 
in many respects to that of the striated muscle, except that the duration of 
the former is considerably longer than the latter. 

Action of Successive Stimuli.—If a series of successive stimuli be 
applied to a muscle, the effect will be different according to the rapidity 
with which they follow each other. If the second stimulus be applied at 
the termination of the contraction, due to the first stimulus, a second con¬ 
traction follows, similar in all respects to the first. A third stimulus pro¬ 
duces a third contraction, and so on until the muscle becomes exhausted. 
If the second stimulus be applied during either of the two periods of the 
first contraction, the effects of the two stimuli will be added together and 
the second contraction will add itself to the first. The maximum contrac¬ 
tion is obtained when the second stimulus is applied -fo of a second after 
the first. 

Tetanus.—When a series of stimuli are applied to a muscle following 
each other with medium rapidity, the muscle does not get time to relax in 
the intervals of stimulation, but remains in a state of vibratory contraction, 
which may be regarded as incipient tetanus, or clonus. As the stimulation 
increases in frequency the vibrations become invisible, being completely 
fused together. There is, nevertheless, during the tetanic condition a series 
of continuous contractions and relaxations taking place. After a varying 
length of time the muscle becomes fatigued, and, notwithstanding the stim¬ 
ulation, begins slowly to elongate. The number of stimuli necessary per 
second for the production of tetanus varies in different animals; e.g ., 2 to 3 
for muscles of the tortoise, 10 for muscles of the rabbit, 15 to 20 for the 
frog, 70 to 80 for the birds, 330 to 340 for insects. 

A Voluntary Contraction in man may be regarded as a state of 
tetanus, for if the curve of a voluntary movement be examined it will be 


50 


HUMAN PHYSIOLOGY. 


found to consist of intermittent vibrations. The simplest voluntary move¬ 
ment of a muscle, however rapidly it may take place, lasts longer than a 
single muscular contraction due to an induction shock. The most rapid 
voluntary contraction is the result of from 2.5 to 4 stimulations per second 
and has a duration of from 0.041 to 0.064 of a second. A continuous 
voluntary contraction is an incomplete tetanus. The number of stimuli 
sent to the muscles is, on the average, 16 to 18 for rapid contractions, 8 to 12 
for slow contractions. 

The Production of Heat and its Relation to Mechanical Work.— 
The transformation of energy which takes place during a muscular con¬ 
traction, and which is dependent upon chemical changes occurring at that 
time, manifests itself as heat and mechanical work. While heat is being 
evolved continuously during the passive condition of muscles, the amount 
of heat is largely increased during general muscular contraction. A skele¬ 
tal muscle of a frog, e.g., the gastrocnemius, when removed from the body 
shows after tetanization an increase in its temperature of from 0.14 0 to 
o.l8° C , and after a single contraction of from o.ooi° to 0.005° C. While 
every muscular contraction is attended by an increase in heat production, 
the amount so'produced will vary in accordance with certain conditions, e.g., 
tension, work done, fatigue, circulation of blood, etc. 

Tension .—The greater the tension of a muscle, the greater, other con¬ 
ditions being equal, is the amount of heat evolved. When the ends of a 
muscle are fastened so that no shortening is possible during stimulation the 
maximum of heat production is reached. In the tetanic state the large in¬ 
crease in temperature is due to the tension of antagonistic and strongly con¬ 
tracted muscles. The evolution of heat, therefore, bears a relation to the 
resistance against which the muscle is acting. 

Mechanical Work .—If a muscle contracts loaded by a weight just suffi¬ 
cient to elongate it to its original length, heat is evolved, but no mechanical 
work is done, all the energy liberated manifesting itself as heat. When 
the weight which has been lifted is removed from the muscle at the height 
of contraction, external work is done. In this case the amount of heat 
liberated is less, owing to the work done, for some of the heat generated is 
transformed into mechanical motion. According to the law of the con¬ 
servation of energy, the amount of heat disappearing should correspond in 
heat units to the number of foot pounds produced by muscular contraction. 

Muscle Sound.—Providing a muscle be kept in a state of tension 
during its contraction, the intermittent variations of its tension cause the 
muscle to emit an audible sound. If the muscle be tetanized by induction 


GENERAL PHYSIOLOGY OF MUSCULAR TISSUE. 


51 


shocks, the pitch of the sound corresponds with the number of stimuli per 
second. A voluntary contraction is attended by a tone having a vibration 
frequency of about 36 per second, which is, however, the first overtone of 
the true muscle tone, which is caused by a contraction frequency of about 
18 per second. This low tone is inaudible, from the low rate of vibrations 
per second. 

Muscular Fatigue.—Prolonged or excessive muscular activity is fol¬ 
lowed by a diminution in the power of producing work and in increase in 
the duration of the muscular contractions. Fatigue is accompanied by a 
feeling of stiffness, soreness, and lassitude, referable to the muscles them¬ 
selves. In the early stages of muscular fatigue, the contractions increase in 
height and duration, to be followed by a progressive decrease in height, 
but an increase in duration, until the muscle becomes exhausted. The 
cause of the fatigue is the production and accumulation of decompo¬ 
sition products, such as phosphoric acid and phosphate of potassium, C 0 2 , 
etc. A fatigued muscle is rapidly restored by the injection of arterial 
blood. 

Work Done.—Muscles are machines capable of doing a certain amount 
of work, by which is meant the raising of a weight against gravity or the 
overcoming of some resistance. The work done is calculated by multiply¬ 
ing the weight by the distance through which it is raised. Thus, if a 
muscle shortens 4 millimeters and raises 250 grammes, it does work equal 
to 1000 milligram-meters, or 1 gram meter. If a muscle contracts with¬ 
out being weighted no work is done. Equally, when the muscle is over¬ 
weighted so that it is unable to contract, no work is done. The amount of 
work a muscle can do will depend upon the area of its transverse section, 
the length of its fibers, and the amount of the weight. The amount of work 
a laborer of 70 kilograms weight performs in 8 hours averages 105,605 
kilogram-meters, or 340.2 foot tons. 


SPECIAL PHYSIOLOGY OF MUSCLES. 

The individual muscles of the axial and appendicular portions of the 
body are named with reference to their shape, action, structure, etc .; e.g ., 
deltoid, flexor, penniform, etc. In different localities, a group of muscles 
having a common function is named in accordance with the kind of motion 
it produces or gives rise to ; e. g., groups of muscles which alternately 
bend or straighten a joint, or alternately diminish or increase the angular 


52 


HUMAN PHYSIOLOGY. 


distance between two bones, are known respectively as flexors and extensors ; 
such muscular groups are in association with ginglymus joints. Muscles 
which turn the bone to which they are attached around its own axis without 
producing any great change of position are known as rotators , and are in as¬ 
sociation with the enartlirodial, or ball-and-socket joints. Muscles which 
impart an angular movement of the extremities to and from the median line 
of the body are termed abductors and adductors. 

In addition to the actions of individual groups of muscles in causing 
special movements in some regions, several groups of muscles are coordi¬ 
nated for the accomplishment of certain definite functions; e. g ., muscles of 
respiration, mastication, expression. The coordination of axial and appen¬ 
dicular muscles enables the individual to assume certain postures, such as 
standing and sitting; to engage in various acts of locomotion, as walking, 
running, swimming, etc. 

Levers.—The function or special mode of action of individual muscles 
can only be understood when the bones with which they are connected are 
regarded as levers whose fulcra or fixed points lie in the joints where the 
movement takes place, and the muscles as sources of power for imparting 
movement to the levers with the object of overcoming resistance or raising 
weights. 

In mechanics, levers of three kinds or orders are recognized, according 
to the relative position of the fulcrum or axis 
of motion, the applied power, and the weight 
to be moved. See Fig. 3. 

In levers of the fii'st order the fulcrum, F, 
lies between the weight or resistance, W, and 
the power or moving force, P. The distance 
PF is known as the power arm, the distance 
WF as the weight arm. As an example of this 
form of lever in the human body may be men¬ 
tioned (1) the elevation of the trunk from the 
flexed position. The axis of movement, the 
fulcrum, lies in the hip joint; the weight, that of the trunk, acting as if con¬ 
centrated at its center of gravity, placed between the shoulders; the power, 
the contracting muscles attached to the tuberosity of the ischium. The 
opposite movement is equally one of the first order, but the relative positions 
of P and W are reversed. (2) the skull in its movements backward and 
forward upon the atlas. 

In levers of the second order the weight lies between the power and 
the fulcrum. As an illustration of this form of lever may be mentioned (1) 


W 


Fig. 3. 

F 


w 

A 

P 

F 

9 

1 

A 

W 

p 

• 


1 F 


P A 


(>) 

(*) 

(3) 


THE THREE ORDERS OF LEVERS. 





SPECIAL PHYSIOLOGY OF MUSCLES. 


53 


the depression of the lower jaw, in which movement the fulcrum is the tem- 
poro-maxillary articulation ; the resistance, the tension of the elevator mus¬ 
cles ; the power, the contraction of the depressor muscles. (2) The raising 
of the body on the toes—F being the toes, W the weight of the body act¬ 
ing through the ankle, P the gastrocnemius muscle acting upon the heel 
bone. 

In levers of the third order the power is applied at a point lying between 
the fulcrum and the weight. As examples of this form of lever may be 
mentioned (1) the flexion of the forearm—F being the elbow joint, 
P the contracting biceps and brachialis anticus muscles applied at their 
insertion, W the weight of the forearm and hand. (2) The extension of 
the leg on the thigh. 

When levers are employed in mechanics, the object aimed at is the over¬ 
coming of a great resistance by the application of a small force acting 
through a great space so as to obtain a mechanical advantage. In the 
mechanism of the human body the reverse generally obtains, viz., the over¬ 
coming of a small resistance by the application of a great force acting 
through a small space. As a result there is a gain in the extent and rapid¬ 
ity of movement of the lever. The power, however, owing to its point of 
application, acts at a great mechanical disadvantage in many instances, 
especially in levers of the third order. 

Postures.—Owing to its system of joints, levers, and muscles, the human 
body can assume a series of positions of equilibrium, such as standing and 
sitting, to which the name posture has been given. In order that the body 
may remain in a state of stable equilibrium in any posture, it is essential 
that the vertical line passing through the center of gravity shall fall within 
the base of support. 

Standing is that position of equilibrium in which aline drawn through 
the center of gravity falls within the area of both feet placed on the ground. 
This position is maintained (i) by firmly fixing the head on the top of the 
vertebral column by the action of the muscles on the back of the neck, (2) 
by making the vertebral column rigid, which is accomplished by the longis- 
simus dorsi and the quadratus lumborum muscles. This having been accom¬ 
plished, the center of gravity falls in front of the tenth dorsal vertebra ; the 
vertical line passing through this point falls behind the jine connecting both 
hip joints. In consequence, the trunk is not balanced on the hip joints, and 
would fall backward were it not prevented by the contraction of the rectus 
femoris muscle and ligaments. At the knees and ankles a similar bal¬ 
ancing of the parts above is brought about by the action of various muscles. 
When the entire body is in the erect or military position, the arms by the 


54 


HUMAN PHYSIOLOGY. 


sides, the center of gravity lies between the sacrum and the last lumbar ver¬ 
tebra and the vertical line touches the ground between the feet and within 
the base of support. 

Sitting erect is a condition of equilibrium in which the body is balanced 
on the tubera ischii, when the trunk and head together form a rigid column. 
The vertical line passes between the tubera. 

Locomotion is the act of transferring the body, as a whole, through 
space, and is accomplished by the combined action of its own muscles. 
The acts involved consist of walking, running, jumping, etc. 

Walking is a complicated act involving almost all the voluntary muscles 
of the body, either for purposes of progression or for balancing the head and 
trunk, and may be. defined as a progression in a forward horizontal direction, 
due to the alternate action of both legs. In walking, one leg becomes, for 
the time being, the active or supporting leg, carring the trunk and head, the 
other the passive but progressive leg, to become in turn the active leg when 
the foot touches the ground. Each leg, therefore, is alternately in an active 
and passive state. 

Running is distinguished from walking by the fact that, at a given mo¬ 
ment, both feet are off the ground and the body is raised in the air. 

While the limits of a compend do not permit of a description of the origin, 
insertion, and mode of action of the individual muscles of the body, it has 
been thought desirable to call attention to a few of the principal muscles 
whose function it is to produce special forms of movement, as well as loco¬ 
motion. (See Fig. 4.) The erect position is largely maintained by the fixation 
of the spinal column and the balancing of the head upon its upper extremity; 
the former is accompanied by the Erector spina muscle, named from its 
function and its fleshy continuations, situated on each side of the vertebral 
column. Arising from the pelvis and lumbar vertebrae, this muscle passes 
upward, and is attached by its continuations to all the vertebrae. Its 
action is to extend the vertebral column and to maintain the erect position. 
The head is balanced upon the top of the vertebral column by the com¬ 
bined action of the trapezius and sub-occipital muscles forming the nape of 
the neck, and by the Sterno-cleido-mastoid muscle. This latter muscle 
arises from the inner third of the clavicle and upper border of the sternum. 
It is inserted into the temporal bone just behind the ear. Its action 
is to flex the head laterally and to rotate the face to the opposite side. 
When both muscles act simultaneously the head and neck are flexed upon 
the thorax. 

The Temporal and Masseter muscles, situated at the side of the head, 
arise respectively from the temporal fossa and the zygomatic arch and are 


Fig. 4. 



SUPERFICIAL MUSCLES OF THE BODY 

































56 


HUMAN PHYSIOLOGY. 


inserted into the ramus of the lower jaw. Their action is to close the 
mouth and assist in mastication. The Occipito-frontalis, the Orbicularis 
palpebrarum , and Orbicularis oris muscles are largely concerned in wrink¬ 
ling the forehead, closing the eyes and mouth, and in giving various ex¬ 
pressions to the face. 

The Deltoid is a thick, triangular muscle covering the shoulder joint. 
Arising from'the outer third of the clavicle, the acromion process and the 
spine of the scapula, its fibers converge to be inserted into the humerus 
just above its middle. Its action is to elevate the arm through a right angle. 
Owing to its point of insertion it acts as a lever of the third order, but, 
notwithstanding the advantageous point of insertion, it acts at a consider¬ 
able disadvantage, owing to the obliquity of its direction. 

The Biceps muscle, situated on the anterior aspect of the arm, arises from 
the upper border of the glenoid fossa and the coracoid process, and is in¬ 
serted into the radius just beyond the elbow joint. Its action is to flex 
and supinate the forearm and to place it in the most favorable position for 
striking a blow. When the forearm is fixed it assists in flexing the arm, as 
in climbing. 

The Triceps muscle, situated on the back of the arm, arises from the 
scapula and the posterior surface of the humerus, and is inserted in the 
olecranon process of the ulna. In its action it directly antagonizes the 
biceps, namely, extending the forearm. In so doing it' acts as a lever of 
the first order. The short distance between the muscular insertion and the 
fulcrum causes it to act at a great mechanical disadvantage, but there is a 
corresponding gain in both speed and range of movement. The muscles 
of the forearm are very numerous. Their action is to impart to the forearm 
and hand a variety of movements, such as pronation, supination, flexion, 
extension, rotation, etc. 

The Pectoralis Major and Minor muscles form the fleshy masses of the 
breast. Arising from the inner half of the clavicle, the side of the sternum, 
and the outer surfaces of the third, fourth, and fifth ribs anteriorly, the mus¬ 
cular fibers converge to be inserted into the humerus and coracoid process. 
Their combined action is to adduct, flex, and rotate the arm inward, and 
to draw the scapula downward and forward, movements necessary to the 
folding of the arms across the chest. 

The Rectus abdominis and the Obliquus externus assist in forming the 
abdominal walls. 

The Glutei muscles are three in number, arranged in layers, and form 
the fleshy masses known as the buttocks. They arise from the side of the 
pelvis and are attached to the femur in the neighborhood of the great tro- 


SPECIAL PHYSIOLOGY OF MUSCLES. 


57 


chanter. Their action is to extend the hips, to raise the body from the 
stooping position, to assist in walking by firmly holding the pelvis on the 
thigh while the opposite leg is advanced in the forward direction. 

The Rectus fetnoris with its associates, the rectus internus and externus 
and crureus, form the fleshy mass on the anterior surface of the thigh. The 
former arises from the anterior part of the ilium, the latter from the femur. 
Their common tendon, which is united to the patella, is continued as the 
ligamentum patellae, which is attached to the upper part of the tibia. The 
action of this muscular group is to extend the leg, to flex the thigh, and to 
raise the entire weight of the body, as in passing from the sitting to the 
erect position. 

The Biceps femoris muscle, situated on the outer and posterior aspect of 
the thigh, arises from the tuber ischii and is inserted into the head of the 
fibula. 

The Semi-membranosus and the Semi-tendinosus muscles, situated on 
the inner and posterior aspect of the thigh, are inserted into the head of 
the tibia. Their combined action is to extend the hips and to flex the knee. 
Acting from below, they assist in raising the body from the stooping 
position. 

The Gastrocnemius muscle forms the enlargement, known as the calf of 
the leg. It arises by two heads from the condyles of the femur. Its ten¬ 
don, the tendo-achillis, is inserted into the posterior surface of the heel 
bone. Its action is to extend the foot and to raise the weight of the body 
in walking and running. On the front of the leg are numerous muscles, 
e.g. y Tibialis anticus, Peroneus longus y etc., the action of which is to flex the 
foot and to antagonize the gastrocnemius. 


FOOD. 

A Food may be defined to be any substance capable of playing a part 
in the nutrition of the body. 

Food is required for the repair of the waste of the tissues consequent on 
their functional activity, for the generation of heat, and the evolution of 
force. 

Hunger and Thirst are sensations which indicate the necessity for 
taking food ; they arise in the tissues at large, and are referred to the 
stomach and fauces, respectively, through the sympathetic nervous system. 

Inanition or Starvation results from an insufficiency or absence of 
E 


58 


HUMAN PHYSIOLOGY. 


food, the physiological effects of which are hunger, intense thirst, intestinal 
uneasiness, weakness, and emaciation; the quantity of carbonic acid ex¬ 
haled diminishes and the urine is lessened in amount; the volume of the 
blood diminishes; a fetid odor is exhaled from the body; vertigo, stupor 
followed by delirium, and at times convulsions, result from a disturbance 
of the nerve centers : a marked fall of the bodily temperature occurs, from 
a diminished activity of the nutritive process. Death usually takes place 
from exhaustion. 

During starvation the loss of different tissues, before death occurs, aver- 
ages T 4 ^, or 40 per cent, of their weight. 

Those tissues which lose more than 40 per cent, are fat, 93.3; blood, 75 ; 
spleen, 71.4; pancreas, 64.1; liver, 52; heart, 44.8; intestines, 42.4; 
muscles, 42.3. Those which lose less than 40 per cent, are the muscular 
coat of the stomach, 39.7; pharynx and esophagus 34.2; skin, 33.3; 
kidneys, 31.9; respiratory apparatus, 22.2; bones, 16.7 ; eyes, 10.; nervous 
system, 1.9. 

The fat entirely disappears, with the exception of a small quantity 
which remains in the posterior portion of the orbits and around the kid¬ 
neys. The blood' diminishes in volume and loses its nutritive properties. 
The muscles undergo a marked diminution in volume and become soft and 
flabby. The net'vous system is last to suffer, not more than two per cent, 
disappearing before death occurs. 

The appearances presented by the body after death from starvation are 
those of anemia and great emaciation ; almost total absence of fat; blood¬ 
lessness ; a diminution in the volume of the organs; an empty condition 
of the stomach and bowels, the coats of which are thin and transparent. 
There is a marked disposition of the body to undergo decomposition, 
giving rise to a very fetid odor. 

The dtcration of life after a complete deprivation of food varies from 
eight to thirteen days, though life can be maintained much longer if a 
quantity of water be obtained. The water is more essential under these 
circumstances than the solid matters, which can be supplied by the organism 
itself. 

The food consumed daily is a heterogeneous compound consisting of 
both nutritious and innutritious portions. The nutritious portions are 
known as the alimentary principles, while the food, as a whole, is known 
as aliment. 

The different alimentary principles which are appropriated by the system 
are combined in different proportions in the various articles of food, and 
are separated from the innutritious substances during the process of diges- 


FOOD. 


59 


tion. They belong to the organic and inorganic worlds, and may be 
classified, according to their chemical composition,as follows:— 


CLASSIFICATION OF ALIMENTARY PRINCIPLES, 

i. Albuminous Group—Nitrogenized, C. O. H. N. S. P. 


PRINCIPLE. WHERE FOUND. 

Myosin syntonin, . Flesh of animals. 

Vitelhn albumin .. Yolk of egg, white of egg. 

Fibrin, globulin, . Blood contained in meat. 

Casein, . Milk, cheese. 

Gluten, . Grain of wheat and other cereals. 

Vegetable albumin, . Soft growing vegetables. 

Legumin, . Peas, beans, lentils, etc. 

Gelatin, . Bones. 


2. Saccharin Group—Non-nitrogenized, C. O. H. 


Cane sugar, beet-root sugar, . . 

Glucose, grape sugar, . 

Inosit, liver sugar, glycogen, . . 

Lactose or milk sugar, . 

Starch, . 


Sugar cane, beets, etc. 

Fruits. 

Muscles, liver, etc. 

Milk. 

Cereals, tuberous roots, and legum¬ 
inous plants. 


3. Oleaginous Group—Non-nitrogenized, C. O. H. 

Animal fats and oils, .... 'I Found in the adipose tissue of ani- 

Stearin, olein, .>• mals, seeds, grains, nuts, fruits, 

Palmitin, fatty acids, . ... ) and other vegetable tissues. 


4. Inorganic Group. Water, sodium and potassium chlorids, sodium, 
calcium, magnesium and potassium phosphates, calcium carbonate and iron. 

5. Vegetable Acid Group. Malic, citric, tartaric, and other acids, 
found principally in fruits. 

6. Accessory Foods. Tea, coffee, alcohol, cocoa, etc. 

The albuminous principles enter largely into the composition of the 
body, and constitute the organic bases of the different tissues; they are 
mainly required for the growth and repair of the tissues. There is good 
reason to believe that the albuminous principles are decomposed in the 
body into fat and urea, and the former when oxidized gives rise to the 
evolution of heat and force, while the latter is eliminated by the kidneys. 
Muscular work, however, does not result from a destruction of the albu¬ 
minous compounds, the oxidation of the carbonaceous compounds, sugars 
and oils, furnishing the force which is transformed by the muscular system 














60 


HUMAN PHYSIOLOGY. 


into motor power. When employed exclusively as food for any length of 
time, the Albuminous substances are incapable of supporting life. 

The saccharin principles are important to the process of nutrition, but 
the changes which they undergo are not fully understood; they form but a 
small proportion of the animal tissues, and by oxidation generate heat and 
force. Starch undergoes conversion into dextrin and grape sugar. 

The oleaginous principles form a large part of the tissues of the body. 
They are introduced into the system as food, and are formed also from a 
transformation of albuminous matter during the nutritive process; they 
enter into the composition of nervous and muscular tissue, and are stored 
up as adipose tissue in the visceral cavities and subcutaneous connective 
tissue, thus giving roundness to the form and preventing, to some extent, 
the radiation of heat. * While they aid in the reconstruction of tissue, they 
mainly undergo oxidation, giving rise to the production of heat and the 
evolution of muscular and nervous force. 

The inorganic principles constitute an essential part of all animal tissues 
and are introduced with the food. 

Water is present in all fluids and solids of the body, holding their 
ingredients in solution, promoting the absorption of new material into the 
blood and tissues, and the removal of waste ingredients. 

Sodium chlorid is an essential constituent of all tissues, regulating the 
passage of fluids through animal membranes (endosmosis and exosmosis). 

Calcium phosphate gives solidity to bones and teeth, constituting more 
than one-half their substance. 

Iron is a constituent of the coloring matter of the blood. 

The vegetable acids are important to nutrition, and tend to prevent the 
scorbutic diathesis. 

The accessory foods also influence the process of nutrition. Tea excites 
the respiratory function, increasing the elimination of carbonic acid. Coffee 
is a stimulant to the nervous system; increases the force of the heart’s 
action, increases the arterial tension, and retards waste. 

Alcohol , when introduced into the system in small quantities , undergoes 
oxidation and contributes to the production of force, and is thus far a food. 
It excites the gastric glands to increased secretion, improves the digestion, 
accelerates the action of the heart, and stimulates the activities of the 
nervous centers. In zymotic diseases, and all cases of depression of the 
vital powers, it is most useful as a restorative agent. When taken in 
excessive quantities it is eliminated by the lungs and kidneys. The meta¬ 
morphosis of the tissue is retarded, the elimination of urea and carbonic 
acid is lessened, the temperature lowered, the muscular powers impaired, 


FOOD. 


61 


and the resistance to depressing external influences diminished. When 
taken through a long period of time, alcohol impairs digestion, produces 
gastric catarrh, disorders the secreting power of the hepatic cells. It also 
diminishes the muscular power and destroys the structure .and composition 
of the cells of the brain and spinal cord. The connective tissue of the body 
increases in amount, and subsequently contracting, gives rise to sclerosis. 

A Proper Combination of different alimentary principles is essential 
for healthy nutrition, no one class being capable of maintaining life for 
any definite length of time. 

The albufninous food in excess promotes the arthritic diathesis, mani¬ 
festing itself as gout, gravel, etc. 

The oleaginous food in excess gives rise to the bilious diathesis, while a 
deficiency of it promotes the scrofulous. 

The farinaceous food , when long continued in excess, favors the rheu¬ 
matic diathesis by the development of lactic acid. 

The Alimentary Principles are not introduced into the body as such, 
but are combined in proper proportions to form compound substances, 
termed foods y e. g., bread, milk, eggs, meat, etc., the nutritive value of each 
depending upon the extent to which these principles exist. 


PERCENTAGE COMPOSITION OF DIFFERENT FOODS. 



WATER. 

ALBUMIN. 

STARCH. 

SUGAR. 

FATS. 

SALTS. 

Bread, . . . 

. . 37 

8.1 

474 

3-6 

1.6 

2-3 

Milk, . . . 

. . 86 

4.1 

. 

5-2 

3-9 

0.8 

Eggs, . . . 

• • 74 

14.0 

. . 

• • 

10.5 

i -5 

Meat, . . . 

• 54 

27.6 

. . 

. , 

15.45 

2.95 

Potatoes, . . 

• • 75 

2.1 

18.8 

3-2 

0.2 

0.7 

Corn, . . . 

. • 14 

11.1 

64.7 

0.4 

8.1 

i -7 

Oatmeal, . , 

. • 15 

12.6 

584 

5-4 

5-6 

3 

Turnips, . . 

• 9 i 

1.2 

5 -i 

2.1 

• • 

6 

Carrots, . . 

• 8 1 

i -3 

8.4 

6.1 

0.2 

1.0 

Rice, . . . 

. • ! 3 

6.3 

79.1 

0.4 

0.7 

o -5 


The Amount of Food required in 24 hours is estimated from the total 
quantity of carbon and nitrogen excreted from the body in 24 hours; these 
two elements representing the waste or destruction of the carbonaceous and 
nitrogenized compounds. It has been determined by experimentation that 
about 4600 grains of carbon and about 300 grains of nitrogen are elimi¬ 
nated from the body daily, the ratio being about 15 to I. That the body 
may be kept in its normal condition, a proper proportion of carbonaceous 
(bread) to nitrogenized (meat) food should be observed in the diet. 





62 


HUMAN PHYSIOLOGY. 


The method of determining the proper amounts of both kinds of food is 
as follows:— 

iooo grains of bread (2 oz). contain 300 grs. C. and 10 grs. N. 

To obtain the • requisite amount of nitrogen from bread, 30,000 grains, 
or about 4 lbs., containing 900 grains of carbon and 300 of nitrogen, 
would have to be consumed. Under such a diet there would be a large 
excess of carbon, which would be undesirable. On a meat diet the reverse 
obtains:— 

1000 grains of meat (2 oz.) contain 100 grs. C. and 30 grs. N. 

To obtain the requisite amounts of carbon from meat, 45,000 grains, or 
about 6^1bs., containing 4500 grains of carbon and 1350 grains of nitro¬ 
gen, would have to be consumed. Under such circumstances there would 
arise an excess of nitrogen in the system, which would be equally undesir¬ 
able and injurious. By combining these two articles, however, in proper 
proportion, the requisite amounts of carbon and nitrogen can be obtained 
without any excess of either, e. g.: — 

2 lbs. of bread contain 4630 grs. C. and 154 grs. N. 
meat « 463 “ “ “ 154 “ “ 

5093 C. 308 N. 

The amount of carbon and nitrogen necessary to compensate for the loss 
to the system daily would be contained in the above amount of food. As 
about oz. or butter are consumed daily, the quantity of bread can 

be reduced to 19 oz. In the quantities of bread and meat above mentioned, 
there are 4.2 oz. albumin, 9.3 sugar and starch. 


DIGESTION. 

Digestion is a physical and chemical process, by which the food intro¬ 
duced into the alimentary canal is liquefied and its nutritive principles 
transformed by the digestive fluids into new substances capable of being 
absorbed into the blood. 

The Digestive Apparatus consists of the alimentary canal and its 
appendages, viz.: teeth, salivary, gastric, and intestinal glands, liver and 
pancreas. 

Digestion may be divided into seven stages ; prehension, mastication, 
insalivation, deglutition, gastric and intestinal digestion, and defecation. 




DIGESTION. 


63 


Prehension, the act of conveying food into the mouth, is accomplished 
by the hands, lips, and teeth. 

Mastication is the trituration of the food, and is accomplished by the 
teeth and lower jaw, under the influence of muscular contraction. When 
thoroughly divided, the food presents a greater surface for the solvent 
action of the digestive fluids, thus aiding the general process of digestion. 

The Teeth are thirty-two in number, sixteen in each jaw, and divided 
into four incisors or cutting teeth, two canines, four bicuspids, and six 
molars or grinding teeth; each tooth consists of a crown covered by 
enamel, a neck, and a root surrounded by the crusta petrosa, and imbedded 
in the alveolar process; a section through a tooth shows that its substance 
is made of dentine, in the center of which is the pulp cavity, containing 
blood-vessels and nerves. 

The lower jaw is capable of making a downward and an upward, a 
lateral and an antero-posterior movement, dependent upon the construction 
of the temporo-maxillary articulation. 

The jaw is depressed by the contraction of the digastric, genio-hyoid, 
mylo-hyoid, and platysma myoides muscles; elevated by the temporal, 
masseter, and internal pterygoid muscles; moved laterally by the alternate 
contraction of the external pterygoid muscles; moved anteriorly by the 
pterygoid and posteriorly by the united actions of the geniohyoid, mylo¬ 
hyoid, and posterior fibers of the temporal muscle. 

The food is kept between the teeth by the intrinsic and extrinsic mus¬ 
cles of the tongue from within, and the orbicularis oris and buccinator 
muscles from without. 

The Movements of Mastication, though originating in an effort of 
the will and under its control, are, for the most part, of an automatic or 
reflex character, taking place through the medulla oblongata and induced 
by the presence of food within the mouth. The nerves and nerve centers 
involved in this mechanism are shown in the following table:— 


NERVOUS CIRCLE OF MASTICATION. 


EFFERENT OR MOTOR NERVES 

1. 3d branch of 5th pair. 

2. Hypo-glossal. 

3. Facial. 


AFFERENT OR EXCITOR NERVES. 

1. Lingual branch of 5th pair. 

2. Glosso-pharyngeal. 


The impressions made upon the terminal filaments of the sensory nerves 
are transmitted to the medulla; motor impulses are here generated which 


64 


HUMAN PHYSIOLOGY. 


are transmitted through motor nerves to the muscles involved in the move¬ 
ments of the lower jaw. The medulla not only generates motor impulses, 
but coordinates them in such a manner that the movements of mastication 
may be directed toward the accomplishment of a definite purpose. 

Insalivation is the incorporation of the food with the saliva secreted 
by the parotid , sub-maxillary , and sub-lingual glands ; the parotid saliva, 
thin and watery, is poured into the mouth through Steno’s duct; the sub¬ 
maxillary and sub-lingual salivas, thick and viscid, are poured into the 
mouth through Wharton’s and Bartholini’s ducts. 

In their minute structure the salivary glands resemble each other. They 
belong to the racemose variety, and consist of small sacs or vesicles, 
which are the terminal expansions of the smallest salivary ducts. Each 
vesicle or acinus consists of a basement membrane surrounded by blood- 


Fig. 5. 




CELLS OF THE ALVEOLI OF A SEROUS OR WATERY SALIVARY GLAND. 

A. After rest. B. After a short period of activity. C. After a prolonged period of 
activity .—Front Yeo’s Text-Book 0/Physiology. 

vessels and lined with epithelial cells. In the parotid gland the lining cells 
are granular and nucleated; in the sub-maxillary and sub-lingual glands the 
cells are large, clear, and contain a quantity of mucigen. During and after 
secretion very remarkable changes take place in the cells lining the acini, 
which are in some way connected with the essential constituents of the 
salivary fluids. 

In a living serous gland, e. g., parotid, during rest, the secretory cells 
lining the acini of the gland are seen to be filled with fine granules, which 
are often so abundant as to obscure the nucleus and enlarge the cells until 
the lumen of the acinus is almost obliterated (Fig. 5). When the gland 
begins to secrete the saliva, the granules disappear from the outer boundary 
of the cells, which then become clear and distinct. At the end of the 
secretory activity, the cells have become free of granules, have become 
smaller and more distinct in outline. It would seem that the granular 





DIGESTION. 


65 


matter is formed in the cells during the rest, and discharged into the ducts 
during the activity of the gland. 

In the mucous glands, e. g., sub-maxillary and sub-lingual, the changes 
that occur in the cells are somewhat different (Fig. 6). During the inter¬ 
vals of digestion, the cells lining the gland are large, clear, and highly 
refractive, and contain a large quantity of mucigen. After secretion has 
taken place, the cells exhibit a marked change. The mucigen cells have 
disappeared, and in their place are cells which are small, dark, and com¬ 
posed of protoplasm. It would appear that the cells, during rest, elabor¬ 
ate the mucigen which is discharged into the tubules during secretory 
activity, to become part of the secretion. 


Fig. 6 . 



SECTION OF A “MUCOUS” GLAND. 

A. In a state of rest. B. After it has been for some time actively secreting .—After 

Lavdowsky. 


Saliva is an opalescent, slightly viscid, alkaline fluid, having a specific 
gravity of 1.005. Microscopical examination reveals the presence of 
salivary corpuscles and epithelial cells. Chemically it is composed of 
water, proteid matter, a ferment ( ptyalin ), and inorganic salts. The 
amount secreted in 24 hours is about 2 l / 2 lbs. Its function is twofold:— 

' 1. Physical .—Softens and moistens the food, glues it together, and 
facilitates swallowing. 

2. Chernical .—Converts starch into sugar. This action is due to the 
presence of the organic ferment, ptyalin. Ptyalin is an amorphous nitro- 
genized substance, which can be precipitated from the saliva by calcium phos¬ 
phate. Its power of converting starch into sugar is manifested most 
decidedly at the temperature of the living body and in a slightly alkaline 



66 


HUMAN PHYSIOLOGY. 


medium. The conversion of starch into sugar takes place through several 
stages, the nature of which depends upon the structure of the starch 
granule. This consists of two portions, a stroma of cellulose and a con¬ 
tained material, Granulose , which is the more abundant and important 
of the two. When subjected to the action of boiling water the starch granule 
swells up and bursts, forming a viscid, opalescent mass of starch paste. If 
saliva be now added to this paste and kept at a temperature of 104° F., 
for a few minutes, the paste becomes clear and limpid. The first stage in 
the digestion is now complete with the formation of soluble starch. If 
the action of saliva be continued, a number of substances intermediate 
between starch and sugar are formed, to which the name dextrin has been 
given. Among these may be mentioned : I. Erythro-dextrin, which gives 
the reddish-brown color with iodin. As the digestion continues and sugar 
is formed the erythro-dextrin disappears, giving way to 2. Achrod-dextrin , 
which yields no coloration with iodin, but which may be precipitated with 
alcohol. 

The sugar formed by the action of saliva is maltose , the formula for which 
is C 12 H 22 0 11 . A small quantity of dextrose is also formed. 

NERVOUS CIRCLE OF INSALIVATION. 

AFFERENT OR EXCITOR NERVES. EFFERENT OR MOTOR NERVES. 

1. Lingual branch of 5th pair. 1. Auriculo temporal branch of 5th 

2. Glosso-pharyngeal. pair, for parotid gland. 

2. Chorda tympani, for sub-maxil¬ 
lary and sub-lingual glands. 

The centers regulating the secretion are two, viz. : The medulla oblon¬ 
gata and the sub-maxillary ganglion of the sympathetic, the latter acting 
antagonistically to the former. Impressions excited by the food in the 
mouth reach the medulla oblongata through the afferent nerves; motor im¬ 
pulses are there generated which pass outward through the efferent nerves. 

Stimulation of the auriculo-temporal branch increases the flow of saliva 
from the parotid gland; division arrests it. 

Stimulation of the chorda tympani is followed by a dilation of the blood¬ 
vessels of the sub-maxillary gland, increased flow of blood (thus acting as 
a vaso-dilator nerve), and an abundant discharge of a thin saliva; division 
of the nerve arrests the secretion. 

Stimulation of the cervical sympathetic is followed by a contraction of 
the blood-vessels, diminishing the flow of blood (thus acting as a vaso-con- 
strictor nerve), and a diminution of the secretion, which now becomes thick 


DIGESTION. 


67 


and viscid; division of the sympathetic does not, however, completely 
dilate the vessels. There is evidence of the existence of a local vaso¬ 
motor mechanism, which is inhibited by the chorda tympani; exalted by 
the sympathetic. 

Deglutition is the act of transferring food from the mouth into the 
stomach, and may be divided into three stages:— 

1. The passage of the bolus from the mouth.into the pharynx. 

2. From the pharynx into the esophagus. 

3. From the esophagus into the stomach. 

In the 1st stage , which is entirely voluntary, the mouth is closed and 
respiration momentarily suspended; the tongue, placed against the roof 
of the mouth, arches upward and backward, and forces the bolus into the 
fauces. 

In the 2d stage , which is entirely reflex, the palate is made tense and 
directed upward and backward by the levatores-palati and tensores-palati 
muscles; the bolus is grasped by the superior constrictor muscle of the 
pharynx and rapidly forced into the esophagus. 

The food is prevented from entering the posterior nares by the uvula and 
the closure of the posterior half-arches (the palato-pharyngei muscles); 
from entering the larynx by its ascent under the base of the tongue and the* 
action of the epiglottis. 

In the jd stage, the longitudinal and circular muscular fibers, contracting 
from above downward, strip the bolus into the stomach. [For nervous 
mechanism of Deglutition, see Medulla Oblongata.] 

Gastric Digestion.—The stomach is a dilation of the alimentary canal, 
13 inches long, 5 inches deep, having a capacity of about 5 pints; there 
can be distinguished a cardiac and pyloric orifice, a greater and lesser cur¬ 
vature, greater and lesser pouch. 

It possesses three coats :— 

1. Serous, a reflection of the peritoneum. 

2. Muscular, the fibers of which are arranged longitudinally, transversely, 
and obliquely. 

3. Mucous, thrown into folds, forming the rugae. 

Embedded in the mucous coat are immense numbers of mucous and true 
gastric glands. In the pyloric end of the stomach are found the mucous 
glands, which are lined with columnar epithelium throughout their extent. 
In the cardiac end are found the true peptic glands (Fig. 7), the ducts of 
which are also lined with columnar cells, while the secretory parts are lined 
with two distinct varieties of cells. One variety consists of small spheroidal, 


68 


HUMAN PHYSIOLOGY. 


granular cells, which border the lumen of the gland, and are known as the 
chief cells; the other variety consists of large, oval, well-defined granular 
cells, much less abundant, and are situated between the basement membrane 
of the gland-and the chief cells. From their position they have been termed 
parietal cells. During the intervals of digestion the chief cells are pale, 
and the hyaline substance of which they are composed is finely granular. 
During the stage of active secretion the cells become swollen and turbid, and 


Fig. 7. 



are then said to be rich in pepsin. Toward the end of digestion the granules 
disappear, the cells become pale and return to their former size. 

During the intervals of digestion the mucous membrane of the stomach 
is pale and covered with a layer of mucus. Upon the introduction of food, 
the blood-vessels dilate and become filled with blood, and the mucous 
membrane becomes red. At the same time small drops of a fluid, the 
gastric juice, begin to exude upon its surface, which gradually run together 
and trickle down the sides of the stomach. 









DIGESTION. 


69 


The secretion of gastric juice is a reflex act, taking place through the 
central nervous system and called forth in response to the stimulus of food 
in the stomach. That the central nervous system also directly influences the 
production of the secretion is shown by the fact that mental emotion, such as 
fear and anger, will arrest or vitiate the normal secretion. The reflex 
nature of the process can be shown by experimentation upon the pneumo- 
gastric nerve. If during digestion, when the- peristaltic movements are 
active and the gastric mucous membrane flushed and covered with gastric 
juice, the pneumogastric nerves are divided on both sides, the mucous mem 
brane becomes pale, the secretion is arrested, and the peristaltic movements 
become less marked. Stimulation of the peripheral end produces no con¬ 
stant effects ; stimulation of the central end, however, is at once followed 
by dilatation of the vessels, flushing of the mucous membrane, and a re¬ 
establishment of the secretion. It is evident, therefore, that during 
digestion afferent impulses are passing up the pneumogastricsto the medulla; 
efferent impulses, in all probability, pass through the fibers of the sympa¬ 
thetic nervous system to the blood-vessels and glands concerned in the 
elaboration of the gastric juice. After all the nervous connections of the 
stomach are divided, a small quantity of juice continues to be secreted for 
several days. This has been attributed to the action of a local nervous 
mechanism and to the direct action of the food upon the protoplasm of the 
secreting cells. 

The Gastric Juice is a secretion of the true peptic glands, and when 
obtained from the stomach through a fistulous opening, is a clear, straw- 
colored fluid, decidedly acid, with a specific gravity of 1.005 to i.oio. 


COMPOSITION OF GASTRIC JUICE. 


Water, . 975 -°° 

Pepsin,.15.00 

Hydrochloric acid,. 4.78 

Inorganic salts,. 5 22 


1000.00 

The water forms the largest part of the fluid, and holds in solution the 
other ingredients. It results from a transudation from the blood-vessels 
under the increased blood supply. Of the inorganic salts the chlorids of 
sodium and potassium are the most abundant. 

Pepsin is the organic nitrogenized ferment of the gastric juice, and is 
formed during the intervals of digestion by the peptic cells. In the pres- 







70 


HUMAN PHYSIOLOGY. 


ence of a small per cent, of an acid, it acquires the property of converting 
the albumin of the food into albuminose or peptones. 

Hydrochloric Acid is present in small quantity, and gives the juice its 
acidity. In all probability, its production is due to the activity of the 
parietal cells. These two characteristic ingredients of the gastric juice 
exist in a state of combination as hydrochloro-peptic acid, and the presence 
of both is absolutely essential for the complete digestion of the food. 

When the food enters the stomach, it is subjected to the peristaltic action 
of the muscular coat, and thoroughly incorporated with the gastric juice. 
This fluid has a twofold action upon the food: 1st. A physical action, by 
which the fibrous tissues of meats, the cellulose and hard parts of grains 
and vegetables, are dissolved away until the food is disintegrated and 
reduced to the liquid condition. 2d. A chemical action, by which the 
albuminous principles are transformed into peptones. The more important 
foods with their contained albuminous principles are shown on page 59. 

Upon meat the gastric juice has a decidedly disintegrating action. The 
connective tissue is first dissolved, the fibers are separated, the sarcolemma 
softened, and the whole reduced to a grumous, pultaceous mass. Milk 
undergoes coagulation in from ten to fifteen minutes, the casein being 
precipitated in the form of soft flocculi, which are easy of transformation 
into peptone. Upon vegetable tissues, the gastric juice exerts also a dis¬ 
integrating action; the cellulose and woody fibers are dissolved and the 
nutritive principles liberated. Bread undergoes liquefaction quite readily. 

The Principal Action of the gastric juice, however, is to transform the 
different albuminous principles of the food into peptones or albuminose, the 
different stages of which are due to the acid and pepsin respectively. When 
freed from its combination, the hydrochloric acid converts the albumin 
into acid albumin or parapept'one ; while this intermediate product is being 
formed, the pepsin converts it at once into peptone. In order that the 
digestion of albumin may be complete, it is necessary that both the acid 
and pepsin be present in proper quantity. Before digestion, the albumi¬ 
nous principles are insoluble in water and incapable of being absorbed. 
After digestion, they become soluble and are readily absorbed. Peptones 
differ from the albumins, in being— 

1. Diffusible, passing rapidly through the mucous membrane and walls 
of the blood-vessels. 

2. Non-coagulable by heat, nitric or acetic acids ; but are readily precipi¬ 
tated by tannic acid. 

3. Soluble in water and saline solutions. 


DIGESTION. 


71 


4. Assimilable by the blood; when injected into it, they do not reappear 
in the urine. 

Gastric juice exerts no influence either upon grape sugar, cane sugar, 
starch, or fat. 

Gastric Digestion occupies on the average from 3 to 5 hours, but 
varies in duration according to the nature and quantity of the food, exer¬ 
cise, temperature, etc. 

The amount of gastric juice secreted in 24 hours varies, under normal 
conditions, from 8 to 14 pounds. 

Movements of the Stomach.—As soon as digestion commences, the 
cardiac and pyloric orifices are closed; the walls of the stomach contract 
upon the food, and a peristaltic action begins, which carries the food along 
the greater and lesser curvatures, and thoroughly incorporates it with the 
gastric juice. As soon as any portion of the food is digested, it passes 
through the pylorus into the intestine. 


TABLE SHOWING DIGESTIBILITY OF VARIOUS ARTICLES 

OF FOOD. 


HOURS. 

Eggs, whipped,.1 

“ soft boiled,.3 

“ hard boiled,.3 

Oysters, raw,.2 

“ stewed,.3 

Lamb, broiled,.2 

Veal, broiled,.4 

Pork, roasted,. 5 

Beefsteak, broiled,.3 

Turkey, roasted,.2 

Chicken, boiled,.4 

“ fricasseed,.2 

Duck, roasted,.4 

Soup, barley, boiled, ..1 

“ beans, “ 3 

“ chicken, “ 3 

“ mutton, “ 3 

Liver, beef, broiled,.2 

Sausage, “ .3 

Green corn, boiled,. 3 

Beans, “ .2 

Potatoes, roasted,.2 

“ boiled,.3 

Cabbage, “ 4 

Turnips, “ 3 

Beets, “ 3 

Parsnips, “ 2 


MINUTES. 

20 

30 

55 

30 

30 

15 

25 

45 

30 


30 

20 

45 

30 

30 

30 

30 

30 

45 

30 





























72 


HUMAN PHYSIOLOGY. 


Vomiting.—The act of vomiting is usually preceded by nausea and a 
discharge of saliva into the mouth. This is then swallowed, and carries 
into the stomach a quantity of air which facilitates the ejection of the con¬ 
tents of the stomach by aiding the relaxation of the cardiac sphincter. A 
deep inspiration is then taken, during which the lower ribs are drawn in 
and the diaphragm descends and remains contracted. At the same time 
the glottis is closed. A sudden expiratory effort is now made, and the cardiac 
orifice being open, the abdominal muscles contracting, press upon the 
stomach and forcibly eject its contents into the mouth. 

Intestinal Digestion.—The intestine is about 20 feet long, i]/ z inches 
in diameter, and possesses three coats :— 

1. Serous (peritoneal). 

2. Muscular, the fibers of which are arranged longitudinally and trans¬ 
versely. 

3. Mucous, thrown into folds, forming the valvulce conniventes. 

This stage of digestion is probably the most complex and important; here 
the different alimentary principles are further elaborated and prepared for 
absorption into the blood by being acted upon by the intestinal juice, pan¬ 
creatic juice , and bile. 

Throughout the mucous coat are embedded the intestinal follicles, the 
glands of Brunner and Lieberkiihn. They secrete the true intestinal juice , 
which is an alkaline, viscid fluid, composed of water, organic matter, and 
salts. Its function is to convert starch into glucose and assist in the diges¬ 
tion of the albuminoids. 

The Pancreatic Juice is secreted by the pancreas, a flattened gland 
about six inches long, running transversely across the posterior wall of the 
abdomen, behind the stomach ; its duct opens into the duodenum. 

The pancreas is similar in structure to the salivary glands, consisting of 
a system of ducts terminating in acini. The acini are tubular or flask¬ 
shaped, and consist of a basement membrane lined by a layer of cylindrical, 
conical cells, which encroach upon the lumen of the acini. The cells 
exhibit a difference in their structure (Fig. 8), and maybe said to consist 
of two zones, viz., an outer parietal zone , which is transparent and appar¬ 
ently homogeneous, staining rapidly with carmine ; an inner zone , which 
borders the lumen, and is distinctly granular and stains but slightly with 
carmine. These cells undergo changes similar to those exhibited by the 
cells of the salivary glands during and after active secretion. As soon as 
the secretory activity of the pancreas is established, the granules disappear, 
and the inner granular layer becomes reduced to a very narrow border, 


DIGESTION. 


73 


while the outer zone increases in size and occupies nearly the entire cell. 
During the intervals of secretion, however, the granular layer reappears 
and increases in size until the outer zone is reduced to a minimum. It 
would seem that the granular matter is formed by the nutritive processes 
occurring in the gland during rest, and is discharged during secretory 
activity into the ducts and takes part in the formation of the pancreatic 
secretion. 

The pancreatic juice is transparent, colorless, strongly alkaline, and viscid, 
and has a specific gravity of 1.040. It is one of the most important of the 
digestive fluids, as it exerts a transforming influence upon all classes of ali- 


Fig. 8. 



ONE SACCULE OF THE PANCREAS OF THE RABBIT IN DIFFERENT STATES OF ACTIVITY. 

A. After a period of rest, in which case the outlines of the cells are indistinct, and the 
inner zone, i. e., the part of the cells ( a ) next the lumen ( c ), is broad and filled with 
fine granules. B. After the gland has poured out its secretion, when the cell out¬ 
lines (d ) are clearer, the granular zone ( a ) is smaller, and the clear outer zone is wider. 
—From Yeo's Text-Book 0/ Physiology , after Kiihne and Lea. 


mentary principles, and has been shown to contain at least three distinct 
ferments. It has the following composition :— 

COMPOSITION OF PANCREATIC JUICE. 


Water,.900.76 

Albuminoid substances, .. 90-44 

Inorganic salts,. 8.80 


1000.00 

The pancreatic juice is characterized by its action : 1st. Upon starch. 
When starch is subjected to the action of the juice, it is at once transformed 
into glucose; the change takes place more rapidly than when saliva is 
F 









74 


HUMAN PHYSIOLOGY. 


added. This action is caused by the presence of a special ferment, amyl- 
opsin. 2d. Upon albumin. The albuminous bodies are changed by the 
juice into, first, an alkali albumin, and then into peptone. The albumin 
does not swell up, as is the case in gastric digestion, but is gradually cor¬ 
roded and dissolved. This change is due to the presence of the ferment, 
trypsin. Long-continued action of trypsin converts the peptones into two 
crystalline bodies, leucin and tyrosin. 3d. Upon fats. The most striking 
action of the pancreatic juice is the emulsification of the fats or their sub¬ 
division into minute particles of microscopic size. This change takes place 
rapidly and depends upon the alkalinity of the fluid and the quantity of 
albumin present, combined with the intestinal movements. The neutral 
fats are also decomposed into their corresponding fatty acids and glycerin ; 
the acids thus set free unite with the alkaline bases present in the intestine 
and form soaps. This decomposition of the neutral fats is caused by the 
ferment, steapsin. 4th. Upon cane sugar the juice also exerts a special 
influence, converting it readily into glucose. 

The total quantity of this fluid secreted in twenty-four hours has not been 
accurately determined; it varies from one to two pounds ; it is poured out 
most abundantly an hour after meals. 

The Bile has an important influence in the elaboration of the food and 
its preparation for absorption. It is a golden-brown, viscid fluid, having a 
neutral or alkaline reaction and a specific gravity of 1.020. 

COMPOSITION OF BILE. 


Water,.859.2 

Sodium glycocholate, ) 

Sodium taurocholate, J . 9 x -4 

Fa t,. 9.2 

Cholesterin, . 2.6 

Mucus and coloring matter,.29.8 

Salts,. 7.8 


1000.00 

The biliary salts, sodium glycocholate and taurocholate, are characteristic 
ingredients, and are formed in the liver by the process of secretion, from 
materials furnished by the blood. It is probable that they are derived from 
the nitrogenized compounds, though the stages in the process are unknown. 
They are reabsorbed from the small intestine to play some ulterior part in 
nutrition. 

Cholesterin is a product of waste taken up by the blood from the nervous 
tissues and excreted by the liver. It crystallizes in the form of rhombic 









DIGESTION. 


75 


plates, which are quite transparent. When retained within the blood, it gives 
rise to the condition of cholestercemia , attended with severe nervous symp¬ 
toms. It is given off in the feces under the form of stercorin. 

The coloring matters which give the tints to the bile are biliverdin and 
bilirubin , and are probably derived from the coloring matter of the blood. 
Their presence in any fluid can be recognized by adding to it nitric acid 
containing nitrous acid, when a play of colors is observed, beginning with 
green, blue, violet, red, and yellow. 

The Bile is both a secretion and an excretion ; it is constantly being 
formed and discharged by the hepatic ducts into the gall bladder, in which 
it is stored up, during the intervals of digestion. As soon as food enters the 
intestines it is poured out abundantly by the contraction of the walls of the 
gall bladder. 

The amount secreted in 24 hours is about 2pounds. 

Functions of the Bile.—(i) It assists in the emulsification of the fats 
and promotes their absorption. (2) It tends to prevent putrefactive changes 
in the food. (3) It stimulates the secretions of the intestinal glands, and 
excites the normal peristaltic movement of the bowels. 

The digested food, the chyme , is a grayish, pultaceous mass, but as it 
passes through the intestines it becomes yellow, from admixture with the 
bile. It is propelled onward by vermicular motion, by the contraction of 
the circular and longitudinal muscular fibers. 

As the Digested Food passes through the intestines, the nutritious 
matters are absorbed into the blood, and the residue enters the large 
intestine. 

The Feces consist chiefly of indigestible matters, excretin t stercorin , 
and salts, varying in amount from 4 to 7 ozs. in 24 hours. 

Defecation is the voluntary act of extruding the feces from the body, 
accomplished by a relaxation of the sphincter muscle, the contraction of the 
walls of the rectum, assisted by the abdominal muscles. 

The Gases contained in the stomach and small intestine are oxygen, 
nitrogen, hydrogen, and carbonic acid. In the large intestine, carbonic 
acid, sulphuretted and carburetted hydrogen. They are introduced with 
the food, and also developed by chemical changes in the alimentary canal. 
They distend the intestines, aid capillary circulation, and tend to prevent 
pressure. 


76 


HUMAN PHYSIOLOGY. 


ABSORPTION. 

The term absorption is applied to the passage or transference of material 
into the blood from the tissues, from the serous cavities, and from the 
mucous surfaces of the body. The most important of these surfaces, espe¬ 
cially in its relation to the formation of the blood, is the mucous surface of 
the alimentary canal; for it is from this organ that new materials are de¬ 
rived which maintain the quality and quantity of the blood. The absorp¬ 
tion of materials from the interstices of the tissues is to be regarded rather 
as a return to the blood of liquid nutritive material which has escaped 
from the blood-vessels for nutritive purposes, and which, if not returned, 
would lead to an accumulation of such fluid and the development of drop¬ 
sical conditions. 

The anatomical mechanisms involved in the absorptive process are, 
primarily, the lymph spaces, the ly 7 iiph capillaries and blood capillaries; 
secondarily, the lymphatic vessels and larger blood-vessels. 

Lymph Spaces, Lymph Capillaries,’Blood Capillaries.—Every¬ 
where throughout the body, in the intervals of connective tissue bundles, 
and in the interstices of the several structures of which an organ is com¬ 
posed, are found spaces of irregular shape and size, determined largely by 
the nature of the organ in which they are found, which have been termed 
lymph spaces or lacuna , from the fact that during the living condition they 
are continually receiving the lymph which has escaped from the blood¬ 
vessels throughout the body. In addition to the connective tissue lymph 
spaces, various observers have described special lymph spaces in the testicle, 
kidney, liver, thymus gland, and spleen; in all secreting glands between 
the basement membrane and blood-vessels; around blood-vessels (perivas¬ 
cular spaces) and around nerves. The serous cavities of the body, peri¬ 
toneal, pleural, pericardial, etc., may also be regarded as lymph spaces, 
which are in direct communication by open mouths or stomata with the 
lymphatic capillaries. This method of communication is not only true of 
serous membranes, but to some extent also of mucous membranes. The 
cylindrical sheaths and endothelial cells surrounding the brain, spinal cord, 
and nerves can also be looked upon as lymph spaces in connection with 
lymph capillaries. 

The lymphatic capillaries , in which the lymphatic vessels proper take 
their origin, are arranged in the form of plexuses of quite irregular shape. 
In most situations they are intimately interwoven with the blood-vessels, 
from which, however, they can be readily distinguished by their larger 


ABSORPTION. 


77 


caliber and irregular expansions. The wall of the lymph capillary is 
formed by a single layer of epithelioid cells, with sinuous outlines, and 
which accurately dovetail with each other. Iij no instance are valves 
found. In the villus of the small intestine the beginning of the lacteal is 
to be regarded as a lymph capillary, generally club-shaped, which at the 
base of the villus enters a true lymphatic; at this point a valve is present, 
which prevents regurgitation. The lymphatic capillaries anastomose freely 
with each other, and communicate on the one hand with the lymph spaces, 
and on the other with the lymphatic vessels proper. 

As the shape, size, etc., of both lymph spaces and capillaries are deter¬ 
mined largely by the nature of the tissues in which they are contained, it 
is not always possible to separate the one from the other. Their function, 
however, may be regarded as similar, viz.:—the collection of the lymph 
which has escaped from the blood-vessels, and its transmission onward into 
the regular lymphatic vessels. 

The blood capillaries not only permit the escape of the liquid nutritive 
portions of the blood through their delicate walls, but are also engaged in 
the reabsorption of this transudate as well as in the absorption of new 
materials from the alimentary canal. The extensive capillary network 
which is formed by the ultimate subdivision of the arterioles in the sub¬ 
mucous tissue and villi of the small intestine forms an anatomical arrange¬ 
ment well adapted for absorption. It is now well known that in the 
absorption of the products of digestion the blood capillaries are more active 
than the lymphatic capillaries. 

Lymphatic Vessels.—The lymphatic vessels constitute a system of 
minute, delicate, transparent vessels, found in nearly all the organs and tissues 
of the body. Having their origin at the periphery in the lymphatic capil¬ 
laries and spaces, they gradually converge toward the trunk of the body and 
empty into the thoracic duct. In their course they pass through numerous 
small ovoid bodies, the lymphatic glands. 

The lymphatic vessels of the small intestine (the ladeals ) arise within 
the villous processes which project from the inner surface of the intestine 
throughout its entire extent. The wall of the villus is formed by an eleva¬ 
tion of the basement membrane, and is covered by a layer of columnar epi¬ 
thelial cells. The basis of the villus consists of adenoid tissue, fine plexus 
of blood-vessels, unstriped muscular fibers, and the lacteal vessel. The 
adenoid tissue consists of a number of intercommunicating spaces, containing 
leukocytes. The lacteal vessel possesses a thin but distinct wall, composed 
of endothelial plates, with here and there openings, which bring the interior 
of the villus into communication with the spaces of the adenoid tissue. 


78 


HUMAN PHYSIOLOGY. 


The structure of the larger vessels resembles that of the veins, consisting 
of three coats :— 

I. External , composed of fibrous tissue and muscular fibers, arranged 
longitudinally. 2. Middle, consisting of white fibers and yellow elastic 
tissue, non-striated muscular fibers, arranged transversely. 3. Internal , 
composed of an elastic membrane, lined by endothelial cells. 

Throughout their course are found numerous semilunar valves , looking 
toward the larger vessels, formed by a folding of the inner coat and 
strengthened by connective tissue. 

Lymphatic Glands.—The lymphatic glands consist of an external 
capsule composed of fibrous tissue which contains non-striped muscular 
fibers: from its inner surface septa of fibrous tissue pass inward and sub¬ 
divide the gland substance into a series of compartments which communi¬ 
cate with each other. The blood-vessels which penetrate the gland are 
surrounded by fine threads, forming a follicular arrangement, the meshes of 
which contain numerous lymph corpuscles. Between the follicular threads 
and the wall of the gland lies a lymph channel traversed by a reticulum of 
adenoid tissue. The lymphatic vessels after penetrating this capsule pour 
their lymph into this channel, through which it passes; it is then collected 
by the efferent vessels and transmitted onward. The lymph corpuscles 
which are washed out of the gland into the lymph stream are formed, most 
probably, by division of pre-existing cells. 

The Thoracic Duct is the general trunk of the lymphatic system, into 
which the vessels of the lower extremities, of the abdominal organs, of the 
left side of the head, and left arm empty their contents. It is about twenty 
inches in length, arises in the abdomen, opposite the third lumbar vertebra, 
by a dilatation, the receptaculum chyli; ascends along the vertebral column 
to the seventh cervical vertebra, and terminates in the venous system at 
the junction of the internal jugular and subclavian veins on the left side. 
The lymphatics of the right side of the head, of the right arm, and the right 
side of the thorax terminate in the right thoracic duct , about one inch in 
length, which joins the venous system at the junction of the internal jugular 
and subclavian on the right side. 

The general arrangement of the lymphatic vessels is shown in Fig. 9. 

The Blood-Vessels which are concerned in the conduction of fresh 
nutritive material from the alimentary canal have their origin in the elabo¬ 
rate capillary network in the mucous membrane. The small veins which 
emerge from this network gradually unite, forming larger and larger trunks, 
which are known as the gastric, superior and inferior mesenteric veins. 


ABSORPTION. 


79 


Fig. 9. 



DIAGRAM SHOWING THE COURSE OF THE MAIN TRUNKS OF THE ABSORBENT SYSTEM. 

The lymphatics of lower extremities (D) meet the lacteals of intestines (LAC) at the 
receptaculum chyli (RC), where the thoracic duct begins. The superficial vessels 
are shown in the diagram on the right arm and leg (S), and the deeper ones on the 
arm to the left (D). The glands are here and there shown in groups. The small 
right duct opens into the veins on the right side. The thoracic duct opens into the 
union of the great veins of the leftside of the neck (T ).—From Yeo’s Text-Book oj 
Physiology. 




80 


HUMAN PHYSIOLOGY. 


These finally unite to form the portal vein, a short trunk about three inches 
in length. The portal vein enters the liver at the transverse fissure, after 
which it forms a fine capillary plexus ramifying throughout the substance 
of the livar; from this plexus the hepatic veins take their origin, which 
finally empty the blood into the vena cava inferior. (See Fig. io.) 

Absorption of Food.—Physiological experiments have demonstrated 
that the agents concerned in the absorption of new materials from the ali- 


Fig. xo. 



Diagram ot the portal vein (pv) arising in the alimentary tract and spleen (s), and car¬ 
rying the blood from these organs to the liver.— From Yeo’s Text-Book of Physiology. 


mentary canal are: 1st. The blood-vessels of the entire canal, but more 
particularly those uniting to form the portal vein. 2d. The lymphatics 
coming from the small intestine, which converge to empty into the thoracic 
duct. As a result of the action of the digestive fluids upon the different 
classes of food stuffs, albumins, sugars, starches, and fats, there are formed 
peptones , glucose , and fatty emulsion , which differ from the former in being 





























ABSORPTION. 


81 


highly diffusible, a condition essential to their absorption. In order that 
these substances may get into the blood, they must pass through the layer 
of cylindrical epithelial cells and the underlying basement membrane and 
into the lymph spaces of the villi and sub-mucous tissue. The mechanism 
by which the cells effect this passage of the food is but imperfectly under¬ 
stood. Osmosis and filtration are conditions, however, made use of by the 
cells in the absorptive process. 

The products of digestion find their way into the general circulation by 
two routes:— 

1. The water y peptones , glucose, and soluble salts, after passing into the 
lymph spaces of the villi, pass through the wall of the capillary blood-vessel; 
entering the blood, they are carried to the liver by the vessels uniting to 
form the portal vein; emerging from the liver, they are emptied into the 
inferior vena cava by the hepatic vein. 

2. The emulsified fat enters the lymph capillary in the interior of the 
villus; by the contraction of the layer of muscular fibers surrounding it 
its contents are forced onward into the lymphatic vessel or lacteal; thence 
into the thoracic duct, and finally into the circulation at the junction of the 
internal jugular and subclavian veins on the left side. 

Absorption of Lymph.—Similar to the absorption of food from the 
alimentary canal, is the absorption of lymph from the lymph spaces of the 
organs and tissues. During the passage of the blood through the capillary 
blood-vessels, a portion of the liquor sanguinis or plasma or lymph, passes 
through the capillary wall out into the lymph spaces. The tissue cells are 
thus bathed with this new material; from it those substances are selected 
which are necessary for their growth, repair, and all purposes of nutrition. 
An excessof nutritive material, far beyond the needs of the tissues, transudes 
from the blood-vessels, and it is this excess which is absorbed by the lym¬ 
phatics, and returned to the blood by the thoracic duct. It is quite probable 
also that a portion of this transudate is reabsorbed by the blood-vessels. 

Properties and Composition of Lymph and Chyle.—Lymph as 
found in the lymphatic vessels of animals, is a clear, colorless, or opalescent 
fluid, having an alkaline reaction, a saline taste, and a specific gravity of 
about 1.040. It holds in suspension a number of corpuscles, resembling in 
their general appearance the white corpuscles of the blood. Their number 
has been estimated at 8200 per cubic millimeter, though the number varies 
in different portions of the lymphatic system. As the lymph flows through 
the lymphatic gland, it receives a large addition of corpuscles. Lymph 
corpuscles are granular in structure, and measure an i nc ^ 1 i n 


82 


HUMAN PHYSIOLOGY. 


diameter. When withdrawn from the vessels, lymph undergoes a spon¬ 
taneous coagulation, similar to that of the blood, after which it separates in 


serum and clot. 

COMPOSITION. OF LYMPH. 

Water, . 96-536 

Proteids (serum-albumin, fibrin-globulin', .... 1.3^0 

Extractives (urea, sugar, cholesterine), ...... 1-559 

Fatty matters,.a trace. 

Salts,. 0 -585 


100.000 

Chyle.— Chyle is the fluid found in the lymphatic vessels, coming from 
the small intestine after the digestion of a meal containing fat. In the 
intervals of digestion, the fluid of these lymphatics is identical in all respects 
with the lymph found in all other regions of the body. As soon as 
the emulsified fat passes into the lymphatic vessels, and mingles with the 
lymph, it becomes milky in color, and the vessels which previously were 
invisible, become visible, and resemble white threads running between the 
layers of the mesentery. Chyle has a composition similar to that of lymph, 
but it contains, in addition, numerous fatty granules, each surrounded by an 
albuminous envelope. When examined microscopically, the chyle presents 

a fine molecular basis, made up of the finely divided granules of fat. 

* 

COMPOSITION OF CHYLE. 


Water,.902.37 

Albumin,. 35.16 

Fibrin,. 3.70 

Extractives,. 15.65 

Fatty matters,. 36.01 

Salts,.. 7.11 


1000.00 

Forces Aiding the Movement of Lymph and Chyle.—The lymph and 
chyle are continually moving in a progressive manner, from the periphery or 
beginning of the lymphatic system, to the final termination of the thoracic 
duct. The force which primarily determines the movement of the lymph, 
has its origin in the beginnings of the lymphatic vessels, and depends upon 
the difference in pressure here and the pressure in the thoracic duct. The 
greater the quantity of fluid poured into the lymph spaces, the greater will 
be the pressure and consequently the movement. The first movement of 
chyle is the result of a contraction of the muscular fibres within the walls 














BLOOD. 


83 


of the villus. At the time of contraction, the lymphatic capillary is com¬ 
pressed and shortened, and its contents forced onward into the true lym¬ 
phatic. When the muscular fibers relax, regurgitation is prevented by the 
closure of the valve in the lymphatic at the base of the villus. 

As the walls of the lymphatic vessels contain muscular fibers, when they 
become distended, these fibers contract and assist materially in the onward 
movement of the fluid. 

The contraction of the general muscular masses in all parts of the body, 
by exerting an intermittent pressure upon the lymphatics, also hastens the 
current onward; regurgitation is prevented by the closure of valves which 
everywhere line the interior of the vessels. 

The respiratory movements aid the general flow of both lymph and chyle 
from the thoracic duct into the venous blood. During the time of an inspi¬ 
ratory movement, the pressure within the thorax, but outside the lungs, 
undergoes a diminution in proportion to the extent of the movement; as a 
result, the fluid in the thoracic duct outside of the thorax, being under a 
higher pressure, flows more rapidly into the venous system. At the time 
of an expiration, the pressure rises and the flow is temporarily impeded, 
only to begin again at the next inspiration. 


BLOOD. 

The Blood is a nutritive fluid containing all the elements necessary for 
the repair of the tissues; it also contains principles of waste absorbed from 
the tissues, which are conveyed to the various excretory organs and by them 
eliminated from the body. 

The total amount of blood in the body is estimated to be about one-eighth 
of the body weight; from 16 to 18 pounds in an individual of average physi¬ 
cal development. The quantity varies during the 24 hours ; the maximum 
being reached in the afternoon, the minimum in the early morning hours. 

Blood is a heterogeneous, opaque, red fluid, having an alkaline reaction, 
a saline taste, and a specific gravity of 1.055. 

The opacity is due to the refraction of the rays of light by the elements 
of which the blood is composed. The color varies in hue, from a bright 
scarlet in the arteries to a deep purple in the veins, due to the presence of 
a coloring matter, hemoglobin , in different degrees of oxidation. 

The alkalinity is constant, and depends upon the presence of the alka¬ 
line sodium phosphate, Na 2 HP 0 4 . 

The saline taste is due to the amount of sodium chlorid present. 


84 


HUMAN PHYSIOLOGY. 


The specific gravity ranges within the limits of health, from 1.045 to 1.075. 

The odor of the blood is characteristic, and varies with the animal from 
w T hich it is drawn, due to the presence of caproic acid. 

The temperature of the blood ranges from 98° Fahr. at the surface to 107° 
Fahr. in the hepatic vein; it loses heat by radiation and evaporation as it 
approaches the extremities, and as it passes through the lungs. 

Blood Consists of Two Portions :— 

1. The liquor sanguinis or plasma , a transparent, colorless fluid, in 
which are floating— 

2. Red and white corpuscles ; these constituting by weight less than one- 
half, 40 per cent., of the entire amount of blood. 

COMPOSITION OF PLASMA. 


DALTON. 

Water,.902.00 

Albumin,.* . . • . 53 *°° 

Paraglobulin,.22.00 

Fibrinogen,. . 3.00 

Fatty matters, . 2.50 

Crystallizable nitrogenous matters,.4.00 

Other organic matter,. 5 00 

Mineral salts,.1.8.50 


1000.00 

Water acts as a solvent for the inorganic matters and holds in suspension 
the corpuscular elements. 

Albumin is the nutritious principle of the blood; it is absorbed by the 
tissues to repair their waste and is transformed into the organic basis char. 
acteristiQ of each structure. 

Paraglobin or fibrinoplastin is a soft amorphous substance precipitated 
by sodium chlorid in excess, or by passing a stream of carbonic acid 
through dilute serum. 

Fibrinogen can also be obtained by strongly . diluting the serum and 
passing carbonic acid through it for a long time, when it is precipitated as 
a viscous deposit. 

Fatty matter exists in small proportion, except in pathological conditions 
and after the ingestion of food rich in oleaginous matters; it soon disap¬ 
pears, undergoing oxidation, generating heat and force, or is deposited as 
adipose tissue. 

Sugar is represented by glucose, a product of the digestion of saccharin 
matter and starches in the alimentary canal; glycogenic matter is derived 
from the liver. 











BLOOD. 


85 


The saline constituents aid the process of osmosis, give alkalinity to the 
blood, promote the absorption of carbonic acid from the tissues into the 
blood, and hold other substances in solution; the most important are the 
sodium and potassium chlorids, the calcium and magnesium phosphates. 

Excrementitious matters are represented by carbonic acid, urea, creatin, 
creatinin, urates, oxalates, etc.; they are absorbed from the tissues by the 
blood and conveyed to the excretory organs, lungs, kidneys, etc. 

Gases. —Oxygen, nitrogen, and carbonic acid exist in varying proportions. 


BLOOD CORPUSCLES. 

The corpuscular elements of the blood occur under two distinct forms, 
which, from their color, are known as the red and white corpuscles. 

The red corpuscles , as they float in a thin layer of the liquor sanguinis, 
are of a pale straw color; it is only when aggregated in masses that they 
assume the bright red color. In form they are circular and biconcave; 
they have an average diameter of the °f an inch- • 

In mammals, birds, reptiles, amphibia, and fish the corpuscles vary in 
size and number, gradually becoming larger and less numerous as the scale 
of animal life is descended, e.g. :— 


TABLE SHOWING COMPARATIVE DIAMETER OF RED 
CORPUSCLES. 

Mammals. Birds. Reptiles. Amphibia. Fish. 

Man, 33*33 Eagle, isYz Turtle, tsst Erog, nVg Perch, 3353 

Chimpanzee, Owl, 17*33 1 ortoise, xiteis ’load, rc?s Carp, 5 t?t 

Ourang, 3353 Sparrow, 5^5 Lizard, 7333 Proteus, 333 Pike, 3033 

Hog, 3353 Swallow, 5^3 Viper, jPri Siren, 533 Eel, 1755 

Cat, *5*3* Pigeon, Amphiuma, 

Hog, 53*33 Turkey, 5^3 

Horse, jsW Goose, 

Ox, 53W Swan, is*ss 


In man and the mammals the red corpuscles present neither a nucleus nor 
a cell wall, and are universally of a small size. They can be readily 
distinguished from the corpuscles of birds, reptiles, and fish, in which they 
are larger, oval in shape, and possess a well-defined nucleus. 

The red corpuscles are exceedingly numerous, amounting to about 
5,000,000 in a cubic millimeter of blood. In structure they consist of a 
firm, elastic, colorless framework, the stroma , in the meshes of which is 
entangled the coloring matter, the hemoglobin. 


86 


HUMAN PHYSIOLOGY. 


CHEMICAL COMPOSITION OF RED CORPUSCLES. 


Water,.688.00 

Globulin,.282.22 

Hemoglobin,.16.75 

Fatty matter,. 2 3 1 

Extractives,. 2 -6o 

Mineral salts,. 8.12 


1000.00 

Hemoglobin , the coloring matter of the corpuscles, is an albuminous com¬ 
pound, composed of C. O. H. N. S. and iron. It may exist either in an 
amorphous or crystalline form. When deprived of all its oxygen, except 
the quantity entering into its intimate composition, the hemoglobin becomes 
dark in color, somewhat purple in hue, and is known as reduced hemoglo¬ 
bin. When exposed to the action of oxygen, it again absorbs a definite 
amount and becomes scarlet in color, and is known as oxy-hemoglobin. 
The amount of oxygen absorbed is 1.76 c.cm. ( T 7 ^ cubic inch) for 1 milli¬ 
gram grain) of hemoglobin. 

It is this substance which gives the color to the venous and arterial 
blood. As the venous blood passes through the capillaries of the lungs, 
the reduced hemoglobin absorbs the oxygen from the pulmonary air and 
becomes oxy-hemoglobin , scarlet in color, and the blood becomes arterial. 
When the arterial blood passes into the systemic capillaries, the oxygen is 
absorbed by the tissues, the hemoglobin becomes reduced, purple in color, 
and the blood becomes venous. A dilute solution of oxy-hemoglobin gives 
two absorption bands between the lines D and E of the solar spectrum. Re¬ 
duced hemoglobin gives but one absorption band, occupying the space 
existing between the two bands of the oxy-hemoglobin spectrum. 

The function of the red corpuscle is, therefore, to absorb oxygen and 
carry it to the tissues ; the smaller the corpuscles and the greater the num¬ 
ber, the greater is the quantity of oxygen absorbed; and, consequently,all 
the vital functions of the body become more active. 

The white corpuscles are far less numerous than the red, the proportion 
being, on an average, about I white to 350 or 400 red; they are globular 
in shape, and measure the of an inch in diameter, and consist of a 
soft, granular, colorless substance, containing several nuclei. 

The white corpuscles possess the power of spontaneous movement, alter¬ 
nately contracting and expanding, throwing out processes of their substance 
and quickly withdrawing them, thus changing their shape from moment to 
moment. These movements resemble those of the amoeba, and for this 










BLOOD. 


87 


reason are termed ameboid. They also possess the capability of moving 
from place to place. In the interior of the vessels they adhere to the inner 
surface, while the red corpuscles move through the center of the stream. 

The white corpuscles are identical with the leucocytes, and are found in 
milk, lymph, chyle, and other fluids. 

Origin of Corpuscles.—The red corpuscles take their origin from the 
mesoblastic cells in the vascular area of the developing embryo. 

In the adult they are produced from colorless nucleated corpuscles re¬ 
sembling the white corpuscles. The spleen is the organ in which they are 
finally destroyed. 

The white corpuscles originate from the leucocytes of the adenoid tissue, 
and subsequently give rise to the red corpuscles and partly to new tissues 
that result from inflammatory action. 


COAGULATION OF THE BLOOD. 

When blood is withdrawn from the body and allowed to remain at rest, 
it becomes somewhat thick and viscid in from three to five minutes ; this 
viscidity gradually increases until the entire volume of blood assumes a 
jelly-like consistence, which occupies from five to fifteen minutes. 

As soon as coagulation is completed, a second process begins, which con¬ 
sists in the contraction of the coagulum and the oozing of a clear, straw- 
colored liquid, the serum , which gradually increases in quantity as the clot 
diminishes in size, by contraction, until the separation is completed, which 
occupies from 12 to 24 hours. 

The changes in the blood are as follows :— 


Before coagulation. 
Living blood. 

After coagulation. 
Dead blood. 


Liq. Sanguinis 
or 

Plasma. 


Water. 

Consisting of j Albumin. 




Corpuscles. Red and white. 

)■ Containing 
Serum. Containing 


Crassamentum. 

Clot or coagulum. / 


Fibrinogen. 

Salts. 


Fibrin. 

Corpuscles. 

Water. 

Albumin. 

Salts. 


The serum, therefore, differs from the liquor sanguinis in not containing 
fibrin. 

In from 12 to 24 hours the upper surface of the clot presents a grayish 




88 


HUMAN PHYSIOLOGY. 


appearance, the buffy coat , which is due to the rapid sinking of the red 
corpuscles beneath the surface, permitting the fibrin to coagulate without 
them, which then assumes a grayish-yellow tint. Inasmuch as the white 
corpuscles possess a lighter specific gravity than the red, they do not sink 
so rapidly, and becoming entangled in the fibrin, assist in forming the buffy 
coat. Continued contraction gives a cupped appearance to the surface of 
the clot. 

Inflammatory states of the blood produce a marked increase in the 
buffed and cupped condition, on account of the aggregation of the corpus¬ 
cles, and their tendency to rapid sinking. 

Nature of Coagulation.—Coagulated fibrin does not preexist in the 
blood, but is formed at the moment blood is withdrawn from the vessels. 
According to Denis, a liquid substance, plasmin, exists in the blood, 
which, when withdrawn from the circulation, decomposes into fibrin and 
met-albumin. 

According to Schmidt, fibrin results from the union of fibrinoplastin 
(paraglobulin) and fibrinogen , brought about by the presence of a third 
substance, the fibrin ferment. 

According to Hammersten and others, the fibrin obtained from the blood 
after coagulation, comes from the fibrinogen alone, the conversion being 
brought about by the presence of a ferment substance, paraglobulin in this 
case having nothing to do with the change. This view is supported by the 
fact that the quantity of fibrin obtained from the blood is never greater than 
the quantity of fibrinogen previously present. The origin of the ferment is 
obscure, but there is reason to believe that it comes from the injured vascu¬ 
lar coats or from the breaking of the white corpuscles. 

Conditions Influencing Coagulation.—The process is retarded by 
cold, retention within living vessels, neutral salts in excess, inflammatory 
conditions of the system, imperfect aeration, exclusion from air, etc. 

It is hastened by a temperature of ioo° F., contact with air, rough sur¬ 
faces, and rest. 

Blood Coagulates in the body after the arrest of the circulation in the 
course of 12 to 24 hours; local arrest of the circulation, from compression 
or a ligature, will cause coagulation, thus preventing hemorrhages from 
wounded vessels. 

The Composition of the Blood varies in different portions of the 
body. The arterial differs from the venous, in being more coagulable, in 
containing more oxygen and less carbonic acid, in having a bright scarlet 


CIRCULATION OF THE BLOOD. 


89 


color, from the union of oxygen with hemoglobin; the purple hue of 
venous blood results from the deoxidation of the coloring matter. 

The blood of the portal vein differs in constitution, according to differ¬ 
ent stages of the digestive process; during digestion it is richer in water, 
albuminous matter, and sugar; occasionally it contains fat; corpuscles are 
diminished, and there is an absence of biliary substances. 

The blood of the hepatic vein contains a larger proportion of red and 
white corpuscles; the sugar is augmented, while albumin, fat, and fibrin 
are diminished. 

Pathological Conditions of the Blood. 

1. Plethora —increase in the volume or quantity of blood. 

2. Anemia —deficiency of red globules with increase of water. 

3. Leucocythemia —increase of white and diminution of red corpuscles. 

4. Glycohemia —excess of sugar in the blood. 

5- Uremia —increase in the amount of urea. 

6. Cholesteremia —an excess of cholesterin in the blood. 

7. Thrombosis and embolism —clotting of blood in the vessels and 
dissemination of coagula. 

8. Lipemia —an excess of fat. 

9. Melanemia —pigment in the blood. 


CIRCULATION OF THE BLOOD. 

The Circulatory Apparatus by which the blood is distributed to all 
portions of the body consists of a central organ, the heart, with which is • 
connected a system of closed vessels, known as arteries, capillaries, and veins. 
Within this system the blood is kept, by the action of the heart, in continual 
movement, distributing nutritious matter to all portions of the body and 
carrying waste matters from the tissues to the various eliminating organs. 

The heart is a hollow muscular organ, pyramidal in shape, measuring 
about 5inches in length, about 3j4 * n breadth, weighing from 10-12 oz. 
in the male and from 8-10 oz. in the female. Situated in the thoracic 
cavity, between the lungs, its base is directed upward, backward, and to the 
right; its apex is directed downward and to the left. 

Pericardium.—The heart is surrounded by a closed fibrous membrane 
called the pericardium. The inner surface of this membrane is lined by a 
serous membrane, which is also reflected over the surface of the heart; 
between the two surfaces of the serous membrane is found a small quantity 
of fluid, the pericardial fluid, which lubricates the surfaces and prevents 
G 


90 


HUMAN PHYSIOLOGY. 


friction during the movements of the heart. The interior of the heart is 
also lined by a serous membrane called the endocardium. 

Cavities of the Heart.—The general cavity of the heart is subdivided 
by a longitudinal septum into a right and left half; each of these cavities is 
in turn subdivided by a transverse constriction into two smaller cavities 
which communicate with each other and are known as the auricles and 
ventricles, the orifice between the auricle and ventricle being known as 
the auriculo-ventricular orifice. The heart therefore consists of four 
cavities, a right auricle and ventricle and a left auricle and ventricle. 

Into the right auricle, the two terminal trunks of the venous system, the 
superior and inferior vence cavce , empty the venous blood which has been 
collected from all parts of the system; from the right ventricle arises the 
pulmonary artery , which, passing into the lungs, distributes the blood to the 
walls of the air cells of the lungs; into the left auricle empty four pulmo¬ 
nary veins which have collected the blood from the lung capillaries; from 
the left ventricle springs the aorta , the general trunk of the arterial sys¬ 
tem whose branches distribute the blood to the entire system. 

The Valves of the Heart.—The valves of the heart are formed by a 
reduplication of the endocardium strengthened by connective tissue. At the 
auriculo-ventricular openings on the right and left sides of the heart respect¬ 
ively are found the tricuspid and mitral valves. The tricuspid valve 
consists of three, the mitral of two cusps or segments which project into 
the interior of the ventricle when it does not contain blood. At their bases 
the segments are united so as to form an annular membrane attached to the 
margin of the orifice. To the free edges of the valves are attached numer¬ 
ous fine threads, the chordce tendinece, which are the tendons of the small 
papillary muscles springing from the walls of the ventricles. 

The Setnilunar Valves. —At the openings of the pulmonary artery and 
the aorta are found three cup-shaped or semilunar valves, the free edges 
of which are directed away from the interior of the heart. The anatomical 
arrangement of the valves is such that upon their closure regurgitation of 
the blood is prevented. 

Movement of the Blood.—The blood within the vascular apparatus is 
in continual movement from the left side of the heart through the arterial 
system, capillaries, and veins to the right side, and from the right side 
through the pulmonary artery, capillaries, and veins to the original point of 
departure. The cause of this movement is the difference of pressure which 
exists between the blood within the aorta and the terminations of the venae 
cavae, and between the blood of the pulmonary artery and the pulmonary veins. 


CIRCULATION OF THE BLOOD. 


91 


The function of the heart is to propel the blood through the blood-ves¬ 
sels, which it does by raising or maintaining this higher pressure in the 


aorta and pulmonary artery. This is ac¬ 
complished by alternate contractions and 
relaxations of its muscular walls. These 
two movements are known respectively as 
the systole and the diastole. 

Course of the Blood through the 
Heart.—The venous blood returned to 
the heart by the superior and inferior venae 
cavae is emptied during the diastole into 
the right a uricl e, in the contraction of 
which it is forced through the right 
auriculo-ventricular opening into the right 
ve ntric le and distends it. Upon the con¬ 
traction of the ventricle the blood is pro¬ 
pelled through the pulmonary artery into 
the lungs, where it undergoes aeration and 
is changed in color. — 

The arterial blood is now collected by 
the pulmonary veins and poured into the 
left auricle; thence it passes into the left 
ventricle, which becomes fully distended. 
Upon the contraction of the ventricle, the 
blood is propelled into the aorta, and by it 
distributed to the system at large, to be 
again returned to the heart by the veins. 

Regurgitation from the ventricles into 
the auricles during the systole is prevented 


Fig. ii. 

K 



by the closure of the tricuspid and mitral 
valves; regurgitation from the pulmonary 
artery and aorta into the ventricles during 
the diastole is prevented by the closure of 
the semilunar valves. 

While there is but one circulation, phy¬ 
siologists frequently divide the circulatory 
apparatus into:— 


SCHEME OF THE CIRCULATION. 
a. Right, b. Left auricle. A. Right, 
B. Left ventricle, i. Pulmonary 
artery. 2. Aorta, i. Area of pul¬ 
monary, K. Area of systemic 
circulation, o. The superior vena 
cava. G. Area supplying the in¬ 
ferior vena cava, u. d, d. Intes¬ 
tine. m. Mesenteric artery, q. 
Portal vein. L. Liver, h. He¬ 
patic vein .—From Landois. 


I. The systemic circulation , which includes the movement of the blood 
from the left side of the heart through the aorta and its branches, through 


the capillaries and veins, to the right side. 











92 


HUMAN PHYSIOLOGY. 


2. The pulmonary circulation , which includes the course of the blood 
from the right side through the pulmonary artery, through the capillaries of 
the lungs and pulmonary veins, to the left side of the heart. 

3. The portal circulation , which includes the portal vein. This is formed 
by the union of the radicles of the gastric, mesenteric, and splenic veins, 
and carries the blood directly into the liver, where the vein again divides 
into a fine capillary plexus from which the hepatic veins arise which empty 
into the ascending vena cava. 

Movements of the Heart.—At each revolution, during the systole, 
the heart hardens and becomes shortened in its long diameter; its apex is 
raised up, rotated on its axis from left to right, and thrown forward against 
the walls of the chest. The impulse of the heart, observed about two 
inches below the nipple, and one inch to the sternal side, between the fifth 
and sixth ribs, is caused mainly by the apex of the heart striking against 
the chest walls, assisted by the distention of the great vessels about the base 
of the heart. 

Sounds of the Heart.—If the ear be placed over the cardiac region, two 
distinct sounds are heard during each revolution of the heart, closely follow¬ 
ing each other and which differ in character. 

The sound coinciding with the systole in point of time, the first sound , 
is long and dull, and caused by the closure -and vibration of the auriculo- 
ventricular valves, the contraction of the walls of the ventricles, and the 
apex beat; the second sound , occurring during the diastole , is short and 
sharp, and caused by the closure of the semilunar valves. 

The capacity of the left ventricle when fully distended is estimated at 
from four to seven ounces. 

The Frequency of the Heart’s Action varies at different periods of 
life, but in the adult male it beats about 72 times per minute. It is 
influenced by age, exercise, posture, digestion, etc. 

Age.—Before birth, the number of pulsations per minute averages 140 

During the first year it diminishes to.128 

During the third year diminishes to. 95 

From the eighth to the fourteenth year averages.84 

In adult life the average is.72 

Exercise and digestion increase the frequency of the heart’s action. 

Posture influences the number of pulsations per minute; in the male, 
standing, the average is 81; sitting, 71; lying, 66;—independent, for the 
most part, of muscular effort. 






CIRCULATION OF THE BLOOD. 


93 


The Rhythmical Movements of the heart are dependent upon : i. 
An inherent irritability of the muscular fiber, which manifests itself as long 
as the nutrition is maintained. 2. The continuous flow of blood through 
its cavities, distending them and stimulating the endocardium. 

The Force Exerted by the Left Ventricle at each contraction has 
been estimated at 52 pounds. If a tube be inserted into the aorta, the pres¬ 
sure there will be sufficient to support a column of blood nine feet or a 
column of mercury six inches in height, the weight in either case being 
about four pounds. The estimation of the force which the heart is required 
to exert to support this column of blood is arrived at by multiplying the 
pressure in the aorta (4 pounds) by the area of the internal surface of the 
left ventricle (about 13 inches), each inch of the ventricle being capable of 
supporting a downward pressure of 4 pounds. 

Work Done by the Heart.—The work done by the heart is estimated 
by multiplying the amount of blood sent out from the right and left ven¬ 
tricles at each contraction by the pressure in the pulmonary artery and 
aorta respectively, e.g.> when the right ventricle contracts, it forces out one- 
quarter pound of blood, and in so doing must overcome a pressure in the 
pulmonary artery sufficient to support a column of blood three feet in 
height; that is, must exert energy sufficient to raise X lb. 3 feet, or X X 3 
or X lb. one foot. When the left ventricle contracts, it sends out X lb. of 
blood, and in so doing, the left ventricle must overcome a pressure in the 
aorta sufficient to support a column of blood nine feet in height; that is, 
must exert energy sufficient to raise X lb. 9 feet, or X X 9 or 2 X ^s. one 
foot. Work done is estimated by the amount of energy required to raise 
a definite weight a definite height, the unit, the foot-pound, being that re¬ 
quired to raise one pound one foot. 

The heart, therefore, at each systole exerts energy sufficient to'raise 3 foot¬ 
pounds, and as it contracts 72 times per minute, it would raise in that 
time 3 X 7 2 or 2I 6 foot-pounds; and in one hour 216 X 60 or 12,960 
foot-pounds; and in 24 hours 12,960 X 2 4 or311,040foot-pounds or 138.5 
foot-tons. 

Influence of the Nervous System upon the Heart.—When the 
heart of a frog is removed from the body, it continues to beat for a variable 
length of time, depending upon the nature of the conditions surrounding 
it. The heart of warm-blooded animals continues to beat but for a very 
short time. The cause of the continued pulsations of the frog heart is the 
presence of nervous ganglia in its substance. These ganglia have not been 


94 


HUMAN PHYSIOLOGY. 


shown to exist in the mammalian heart, but there is reason to believe that 
the nervous mechanism is fundamentally the same. 

The ganglia of the heart are three in number, one situated at the opening 
of the inferior vena cava (the ganglion of Remak), a second situated in 
the auriculo-ventricular septum (the ganglion of Biddle), and a third 
situated in the inter-auricular septum (the ganglion of Ludwig). The first 
two are motor in function and excite the pulsations of the heart; the third 
is inhibitory in function and retards the action of the heart. The actions 
of these ganglia, though for the most part automatic, are modified by im¬ 
pressions coming through nerves from the medulla oblongata. When the 
inhibitory centre is stimulated by muscarin, the heart is arrested in diastole; 
when atropia is applied, the heart recommences to beat, because atropia 
paralyzes the inhibitory center. 

The nerves modifying the action of the heart are the Pneumogastric 
(Vagus) and the Accelerator nerves. 

The pneumogastric nerve , after emerging from the medulla, receives 
motor fibers from the spinal accessory nerve. It then passes downward, 
giving off branches, some of which terminate in the inhibitory ganglion. 
Stimulation of the vagus by increasing the activity of the inhibitory center 
arrests the heart in diastole with its cavities full of blood; but as the stimu¬ 
lation is only temporary, after a few seconds the heart recommences to 
beat; at first the pulsations are weak and feeble, but soon regain their 
original vigor. After the administration of atropia in sufficient doses to de¬ 
stroy the termination of the pneumogastric, stimulation of its trunk has no 
effect upon the heart.- The inhibitory fibers in the vagus are constantly 
in action, for division of the nerve on both sides is always followed by an 
increase in the frequency of the heart’s pulsations. 

The accelerator fibers arise in the medulla, pass down the cord, emerge 
in the cervical region, pass to the last cervical and first dorsal ganglia of 
the sympathetic, and thence to the heart. Stimulation of these fibers causes 
an increased frequency of the heart’s pulsations, but they are diminished in 
force. 


ARTERIES. 

The Arteries are a series of branching tubes conveying blood to all 
portions of the body. They are composed of three coats— 

1. External , formed of areolar and elastic tissue. ' 

2. Middle , contains both elastic and muscular fibers, arranged trans¬ 
versely to the long axis of the artery. The elastic tissue is more abundant 
in the larger vessels; the muscular in the smaller. 


ARTERIES. 


95 


3. Internal , composed of a thin homogeneous membrane, covered with 
a layer of elongated endothelial cells. 

The arteries possess both elasticity and contractility . 

The property of elasticity allows the arteries already full to accommo¬ 
date themselves to the incoming amount of blood, and to convert the 
intermittent acceleration of blood in the large vessels into a steady and 
continuous stream in the capillaries. 

The contractility of the smaller vessels equalizes the current of blood, 
regulates the amount going to each part, and promotes the onward flow 
of blood. 

Blood Pressure.—Under the influence of the ventricular systole, the 
recoil of the elastic walls of the arteries, and the resistance offered by the 
capillaries, the blood is constantly being subjected to a certain amount ot 
pressure. If a large artery of an animal be divided, and a glass tube of 
the same caliber be inserted into its orifice, the blood will rise to a height 
of about nine feet; or if it be connected with a mercurial manometer, the 
mercury will rise to a height of six inches. This height will be a measure 
of the pressure in the vessel. The absolute quantity of mercury sustained 
by an artery can be arrived at by multiplying the height of the column by 
the area of a transverse section of that artery. 

The pressure of the blood is greatest in the large arteries, but gradually 
decreases toward the capillaries. 

The blood pressure is increased or diminished by influences acting upon 
the heart or upon the peripheral resistance of the capillaries, viz.:— 

If, while the force of the heart remains the same, the number of pulsa¬ 
tions per minute increases, thus increasing the volume of blood in the 
arteries, the pressure rises. If the rate remains the same, but the force 
increases, the pressure again rises. Causes that increase the peripheral 
resistance by contracting the arterioles, e.g. y vasomotor nerves, cold, etc., 
produce an increase of the pressure. 

On the other hand, influences which diminish either the volume of the 
blood, or the number of pulsations, or the force of the heart, or the peri¬ 
pheral residence, lower the pressure. 

The Pulse is the sudden distention of the artery in a transverse and 
longitudinal direction, due to the injection of a volume of blood into the 
arteries at the time of the ventricular systole. As the vessels are already 
full of blood, they must expand in order to accommodate themselves to the 
incoming volume of blood. The blood pressure is thus increased, and the 
pressure originating at the ventricle excites a pulse wave , which passes 


96 


HUMAN PHYSIOLOGY. 


from the heart toward the capillaries at the rate of about twenty-nine feet 
per second. It is this wave that is appreciated by the finger. 

The Velocity with which the blood flows in the arteries diminishes 
from the heart to the capillaries, owing to an increase of the united sectional 
area of the vessels, and increases in rapidity from the capillaries toward the 
heart. It moves most rapidly in the large vessels, and especially under 
the influence of the ventricular systole. From experiments on animals, 
it has been estimated to move in the carotid of man at the rate of sixteen 
inches per second, and in the large veins at the rate of four inches per 
second. 

The Caliber of the Blood-vessels is regulated by the vasomotor 
nerves, which have their origin in the gray matter of the medulla oblongata. 
They issue from the spinal cord through the anterior roots of spinal nerves, 
pass through the sympathetic ganglia, and ultimately are distributed to the 
coats of the blood-vessels. They exert at different times a constricting and 
dilating action upon the vessels, thus keeping up the arterial tonus. 

Capillaries.—The capillaries constitute a network of vessels of micro¬ 
scopic size, which distribute the blood to the inmost recesses of the tissues, 
inosculating with the arteries on the one hand and the veins on the other; 
they branch and communicate in every possible direction. 

The diameter of a capillary vessel varies from the to the of 
an inch ; their walls consist of a delicate homogeneous membrane, the 
Toio'S an ^ nc k * n thickness, lined by flattened, elongated, endothelial 
cells, between which, here and there, are observed stomata. 

It is through the agency of the capillary vessels that the phenomena of 
nutrition and secretion takes place, for here the blood flows in an equable 
and continuous current, and is brought into intimate relationship with the 
tissues, two of the essential conditions for proper nutrition. 

The rate of movement in the capillary vessels is estimated at one inch in 
thirty seconds. 

In the capillary current the red corpuscles may be seen hurrying down 
the center of the stream, while the white corpuscles in the still layer adhere 
to the walls of the vessel, and at times can be seen to pass through the 
walls of the vessel by ameboid movements. 

The Passage of the Blood through the capillaries is mainly due to 
the force of the ventricular systole and the elasticity of the arteries; but it 
is probably also aided by a power resident in the capillaries themselves, the 
result of a vital relation between the blood and the tissues. 

The Veins are the vessels which return the blood to the heart; they 


arteries. 


97 


have their origin in the venous radicles, and, as they approach the heart, 
converge to form larger trunks, and terminate finally in the vense cavse. 

They possess three coats— 

1. External , made up of areolar tissue. 

2. Middle , composed of non-striated muscular fibers, yellow, elastic, and 
fibrous tissue. 

3. Internal , an endothelial membrane, similar to that of the arteries. 

Veins are distinguished by the possession of valves throughout their 

course, which are arranged in pairs, and formed by a reflection of the internal 
coat, strengthened by fibrous tissues ; they always look toward the heart, and 
when closed prevent a return of blood in the veins. Valves are most numerous 
in the veins of the extremities, but are entirely absent in many others. 

The Onward Flow of Blood in the veins is mainly due to the action 
of the heart, but is assisted by the contraction of the voluntary muscles and 
the force of respiration. 

Muscular contraction , which is intermittent, aids the flow of blood in the 
veins by compressing them. As regurgitation is prevented by the closure 
of the valves, the blood is forced onward toward the heart. 

Rhythmical movements of veins have been observed in some of the 
lower animals, aiding the onward current of blood. 

During the movement of inspiration the thorax is enlarged in all its 
diameters, and the pressure on its contents at once diminishes. Under 
these circumstances a suction force is exerted upon the great venous trunks, 
which causes the blood to flow with increased rapidity and volume toward 
the heart. 

Venous Pressure.—As the force of the heart is nearly expended in 
driving the blood through the capillaries, the pressure in the venous system 
is not very marked, not amounting in the jugular vein of a dog to more 
than T2 that of the carotid artery. 

The time required for a complete circulation of the blood throughout the 
vascular system has been estimated to be from 20 to 30 seconds, while for 
the entire mass of blood to pass through the heart 58 pulsations would be 
required, occupying 48 seconds. 

The Forces keeping the blood in circulation are— 

1. Action of the heart. 

2. Elasticity of the arteries. 

3. Capillary force. 

4. Contraction of the voluntary muscles upon the veins. 

5. Respiratory movements. 


98 


HUMAN PHYSIOLOGY. 


RESPIRATION. 

Respiration is the function by which oxygen is absorbed into the 
blood and carbonic acid exhaled. The appropriation of the oxygen and 
the evolution of carbonic acid takes place in the tissues as a part of the 
general nutritive process, the blood and respiratory apparatus constituting 
the media by means of which the interchange of gases is accomplished. 

The Respiratory Apparatus consists of the larynx, trachea, and lungs. 

The Larynx is composed of firm cartilages, united together by liga¬ 
ments and muscles ; running antero-posteriorly across the upper opening 
are four ligamentous bands, the two superior, or false vocal cords, and the 
two inferior, or true vocal cords, formed by folds of the mucous membrane. 
They are attached anteriorly to the thyroid cartilages and posteriorly to the 
arytenoid cartilages, and are capable of being separated by the contraction 
of the posterior cricoarytenoid muscles, so as to admit the passage of air 
into and from the lungs. 

The Trachea is a tube from four to five inches in length, three quarters 
of an inch in diameter, extending from the cricoid cartilage of the larynx 
to the third dorsal vertebra, where it divides into the right and left bronchi. 
It is composed of a series of cartilaginous rings, which extend about two- 
thirds around its circumference, the posterior third being occupied by fibrous 
tissue and non-striated muscular fibers, which are capable of diminishing 
its caliber. 

The trachea is covered externally by a tough, fibro-elastic membrane, 
and internally by mucous membrane, lined by columnar ciliated epithelial 
cells. The cilia are always waving from within outward. When the two 
bronchi enter the lungs they divide and subdivide into numerous and 
smaller branches, which penetrate the lung in every direction until they 
finally terminate in the pulmonary lobules. 

As the bronchial tubes become smaller their walls become thinner; the 
cartilaginous rings disappear, but are replaced by irregular angular plates 
of cartilage; when the tube becomes less than the of an inch in diame¬ 
ter they wholly disappear, and the fibrous and mucous coats blend together, 
forming a delicate elastic membrane, with circular muscular fibers. 

The Lungs occupy the cavity of the thorax, are conical in shape, of a 
pink color and a spongy texture. They are composed of a great number of 
distinct lobules, the pulmonary lobules , connected together by interlobular 
connective tissue. These lobules vary in size, are of an oblong shape, and 


RESPIRATION. 


99 


are composed of the ultimate ramifications of the bronchial tubes, within 
which are contained the air vesicles or cells. The walls of the air vesicles, 
exceedingly thin and delicate, are lined internally by a layer of tessellated 
epithelium, externally covered by elastic fibers, which give the lungs their 
elasticity and distensibility. 


Fig. 12. 


The Venous Blood is distributed to the lungs for aeration by the pul¬ 
monary artery, the terminal branches of which form a rich plexus of capil¬ 
lary vessels surrounding the air cells; the air and blood are thus brought 
into intimate relationship, being separ¬ 
ated only by the delicate walls of the 
air cells and capillaries. 

The thoracic cavity in which the re¬ 
spiratory organs are lodged is of a coni¬ 
cal shape, haying its apex directed up¬ 
ward, its base downward. Its frame¬ 
work is formed posteriorly by the spinal 
column, anteriorly by the sternum, and 
laterally by the ribs and costal cartilages. 

Between and over the ribs lie muscles, 
fascia and skin; above the thorax is 
completely closed by the structures pass¬ 
ing into it and by the cervical fascia, 
and skin ; below it is closed by the dia¬ 
phragm. It is therefore an air-tight 
cavity. 

The Pleura.—Each lung is sur¬ 
rounded by a closed serous membrane, 
the pleura, one layer of which, the vis¬ 
ceral, is reflected over the lung, the 
other, the parietal , reflected over the 
wall of the thorax; between the two 
layers is a small amount of fluid which prevents friction during the play of 
the lungs in respiration. 

Owing to the elastic tissue which is present in the lungs, they are very 
readily distensible, so much so, indeed, that the pressure of the air inside 
the trachea and lungs is sufficient to distend them until they completely 
fill all parts of the thoracic cavity not occupied by the heart and great 
vessels. The elastic tissue endows them not only with distensibility, 
but also with the power of elastic recoil, by which they are enabled to 
accommodate themselves to all variations in the size of the thoracic cavity. 



OF THE RESPIRATORY 
ORGANS. 


The windpipe leading down from the 
larynx is seen to branch into two 
large bronchi, which subdivide after 
they enter their respective lungs. 





100 


HUMAN PHYSIOLOGY. 


When the' chest walls recede, the air within the lungs expands and 
presses them against the ribs; when the chest walls contract, the air 
being driven out, the elastic tissue recoils and the lungs return to their 
original condition. The movements of the lungs are therefore entirely 
passive. 

As the capacity of the chest in a state of rest is greater than the volume 
of the lungs after they are collapsed, it is quite evident that in the living 
condition the lungs are distended and in a state of elastic tension, which 
is greater or less in proportion as the thoracic cavity is increased or dimin¬ 
ished in size. The elastic tissue, always on the stretch, is endeavoring to 
puli the visceral layer of the pleura away from the parietal layer, but is 
antagonized by the pressure of the air within the air passages. This con¬ 
dition of things persists as long as the thoracic cavity remains air tight; but 
if an opening be made in the thoracic wall, the pressure of the external air 
which was previously supported by the practically rigid walls of the thorax 
now presses upon the lung with as much force as the air within the lung. 
The two pressures being neutralized, there is nothing to prevent the elastic 
tissue from recoiling, driving the air out, and collapsing. The elastic ten¬ 
sion of the lungs can be readily measured in man after death by inserting 
a manometer into the trachea. Upon opening the thorax and allowing the 
tissue to recoil, the air presses upon the! 1 mercury and elevates it, the extent 
to which it is raised being the .index of the pressure. Hutchinson calcu¬ 
lated the pressure to be one-half pound to the square inch of the lung 
surface. 

Respiratory Movements.—The movements of respiration are two, and 
consist of an alternate dilatation and contraction of the chest, known as 
inspiration and expiration. 

1. Inspiration is an active process, the result of the expansion of the 
thorax, whereby air is introduced into the lungs. 

2. Expiration is a partially passive process, the result of the recoil of 
the elastic walls of the thorax, and the recoil of the elastic tissue of the 
lungs, whereby the carbonic acid is expelled. 

In Inspiration the chest is enlarged by an increase in all its diameters, 
viz.:— 

1. The vertical is increased by the contraction and descent of the dia¬ 
phragm when it approximates a straight line. 

2. The anteroposterior and transverse diameters are increased by the 
elevation and rotation of the ribs upon their axes. 

In ordinary tranquil inspiration the muscles which elevate the ribs and 


RESPIRATION. 


101 


thrust the sternum forward, and so increase the diameters of the chest, are 
the external intercostals, running from above downward and forward, the 
sternal portion of the internal intercostals , and the levatores costarum. 

In the extraordinary efforts of inspiration certain auxiliary muscles are 
brought into play, viz. : the sterno-mastoid, pe dor ales, serratus magnus , 
which increase the capacity of the thorax to its utmost limit. 

In Expiration the diameters of the chest are all diminished, viz.:— 

1. The vertical , by the ascent of the diaphragm. 

2. The antero-posterior , by a depression of the ribs and sternum. 

In ordinary tranquil expiration the diameters of the thorax are dimin¬ 
ished by the recoil of the elastic tissue of the lungs and the ribs; but in 
forcible expiration the muscles which depress the ribs and sternum, and 
thus further diminish the diameter of the chest, are the internal intercostals, 
the infracostals , and the triangularis sterni. 

In the extraordinary efforts of expiration certain auxiliary muscles are 
brought into play, viz.: the abdominal and sacro-lumbalis muscles , which 
diminish the capacity of the thorax to its utmost limit. 

Expiration is aided by the recoil of the elastic tissue of the lungs and ribs 
and the pressure of the air. 

Movements of the Glottis.—At each inspiration the rim a-glottidis is 
dilated by a separation of the vocal cords, produced by the contraction of 
the crico-arytenoid muscles, so as to freely admit the passage of air into the 
lungs : in expiration they fall passively together, but do not interfere with 
the exit of air from the chest. 

Nervous Mechanism of Respiration.—The movements of Respira¬ 
tory muscles, though capable of being modified to a certain extent by 
efforts of the will, are of an automatic character, and called forth by 
nervous impulses emanating from the medulla oblongata. The Respira¬ 
tory center, the so-called vital point, generates the nerve impulses, which, 
traveling outward through the phrenic and intercostal nerves, excite con¬ 
tractions of the diaphragm and intercostal muscles respectively. This 
center is for the most part automatic in its action, though it is capable of 
being modified by impulses reflected to it through various sensory nerves. 

This center may be stimulated— 

1. Directly, by the condition of the blood. An increase of carbonic acid 
or a diminution of oxygen in the blood causes an acceleration of the respi¬ 
ratory movements ; the reverse of these conditions causes a diminution of 
the respiratory movements. 

2 . Indirectly, by reflex action. The medulla may be excited to action 


102 


HUMAN PHYSIOLOGY. 


through the pneumogastric nerve, by the presence of carbonic acid in the 
lungs irritating its terminal filaments; through the fifth nerve, by irritation 
of the terminal branches; and through the nerves of general sensibility. 
In either case this center reflects motor impulses to the respiratory muscles 
through the phrenic , intercostals , inferior laryngeal, and other nerves. 

Types of Respiration.—The abdominal type is most marked in young 
children, irrespective of sex, the respiratory movements being effected by 
the diaphragm and abdominal muscles. 

In the superior costal type , exhibited by the adult female, the respiratory 
movements are more marked in the upper part of the chest, from the 1st to 
the 7th ribs, permitting the uterus to ascend in the abdomen during preg¬ 
nancy without interfering with respiration. 

In the inferior costal type, manifested by the male, the movements are 
largely produced by the muscles of the lower portions of the chest, from the 
7th rib downward, assisted by the diaphragm. 

The respiratory movements vary according to age, sleep, and exercise, 
being most frequent in early life, but averaging 20 per minute in adult life. 
They are diminished by sleep and increased by exercise. There are about 
four pulsations of the heart to each respiratory act. 

During inspiration two sounds are produced; the one, heard in the 
thorax, in the trachea and larger bronchial tubes, is tubular in character; 
the other, heard in the substance of the lungs, is vesicular in character. 

AMOUNT OF AIR EXCHANGED IN RESPIRATION, AND CAPACITY 

OF LUNGS. 

The tidal or breathing volume of air, that which passes in and out of the 
lungs at each inspiration and expiration, is estimated at from 20 to 30 cubic 
inches. 

The complemental air is that amount which can be taken into the lungs 
by a forced inspiration, in addition to the ordinary tidal volume, and 
amounts to about no cubic inches. 

The reserve air is that which usually remains in the chest after the ordi¬ 
nary efforts of expiration, but which can be expelled by forcible expiration. 
The volume of reserve air is about 100 cubic inches. 

The residual air is that portion which remains in the chest and cannot 
be expelled after the most forcible expiratory efforts, and which amounts, 
according to Dr. Hutchinson, to about 100 cubic inches. 

The Vital Capacity of the chest indicates the amount of air that can 
be forcibly expelled from the lungs after the deepest possible inspiration, 


RESPIRATION. 


103 


and is an index of an individual’s power of breathing in disease and pro¬ 
longed severe exercise. The combined amounts of the tidal, the comple- 
mental, and reserve air, 230 cubic inches, represents the vital capacity of an 
individual 5 feet 7 inches in height. The vital capacity varies chiefly with 
stature. It is increased 8 cubic inches for every inch in height above this 
standard, and diminishes 8 cubic inches for each inch below it. 

The Tidal Volume of air is carried only into the trachea and larger 
bronchial tubes by the inspiratory movements. It reaches the deeper 
portions of the lungs in obedience to the law of diffusion of gases, which is 
inversely proportionate to the square root of their densities. 

The ciliary action of the columnar cells lining the bronchial tubes also 
assists in the interchange of air and carbonic acid. 

The entire volume of air passing in and out of the thorax in 24 hours is 
subject to great variation, but can be readily estimated from the tidal 
volume and the number of respirations per minute. Assuming that an 
individual takes into the chest 20 cubic inches at each inspiration, and 
breathes 18 times per minute, in 24 hours there would pass in and out of 
the lungs 518,400 cubic inches, or 300 cubic feet. 

Chemistry of Respiration.—As the inspired air undergoes a change 
in composition during its stay in the lungs which renders it unfit for further 
respiration, it becomes requisite, for the correct understanding of respiration, 
to ascertain the composition of both inspired and expired air. 

Composition of Air.—Chemical analysis has shown that every 100 
vols. of air contains 20.81 vols. of oxygen, and 70.19 vols. of nitrogen, and 
0.03 vol. of carbonic acid. Aqueous vapor is also present, though the 
quantity is variable. The higher the temperature the greater the amount. 

The changes in the air effected by respiration are— 

Loss of oxygen, to the extent of 5 cubic inches per 100 of air, or 1 in 
20. 

Gain of carbonic acid, to the extent of 4.66 cubic inches per 100 of 
air, or .93 inch in 20. 

Increase of water vapor and organic matter. 

Elevation of temperature. 

Increase and at times decrease of nitrogen. 

Gain of ammonia. 

The total quantity of oxygen withdrawn from the air and consumed by 
the body in 24 hours amounts to 15 cubic feet, and can be readily esti¬ 
mated from the amount consumed at each respiration. Assuming that one 
inch of oxygen remains in the lungs at each respiration, in one hour there 


104 


HUMAN PHYSIOLOGY. 


are consumed 1080 inches, and in 24 hours, 25,920 cubic inches or 15 cubic 
feet, weighing 18 oz. To obtain this quantity, 300 cubic feet of air are 
necessary. 

The quantity of oxygen consumed daily is subject to considerable varia¬ 
tions. It is increased by exercise, digestion, and lowered temperature, and 
decreased by the opposite conditions. 

The quantity of carbonic acid exhaled in 24 hours varies greatly. It 
can be estimated in the same way. Assuming that an individual exhales 
•93 + cubic inch at each respiration, in one hour there are eliminated 1008 
cubic inches, and in 24 hours, 24.192 cubic inches or 14 cubic feet, contain¬ 
ing 7 ozs. of pure carbon. 

The exhalation of carbonic acid is increased by muscular exercise, 
nitrogenous food, tea, coffee, and rice, age, and by muscular development ; 
decreased by a lowering of temperature, repose, gin and brandy, and a 
dry condition of the air. 

As there is always more oxygen consumed than carbonic acid exhaled, 
and as oxygen unites with carbon to form an equal volume of carbonic acid, 
it is evident that a certain quantity of oxygen disappears within the body. 
In all probability it unites with the sulphur hydrogen of the food to form 
water. 

The amount of watery vapor which passes out of the body with the 
expired air is estimated at from one to two pounds. 

The organic matter, though slight in amount, gives the odor to the breath. 
In a room with defective ventilation, the organic matter accumulates and 
gives rise to headache, nausea, drowsiness, etc. Long-continued breathing 
of such air produces general ill health. It is not so much the presence of 
C0 2 in increased amount as the presence of organic matter which neces¬ 
sitates thorough ventilation. 

Condition of the Gases in the Blood. 

Oxygen is absorbed from the lungs into the arterial blood by the coloring 
matter, heifioglobin , with which it exists in a state of loose combination, 
and is disengaged during the process of nutrition. 

Carbonic acid, arising in the tissues, is absorbed into the blood, in conse¬ 
quence of its alkalinity, where it exists in a state of simple solution and 
also in a state of feeble combination with the carbonates, soda and potassa, 
forming the bicarbonates. 

Nitrogen is simply held in solution in the plasma. 

Exchange of Gases in the Air Cells.—From the difference in ten¬ 
sion of the oxygen in the air cells (27.44 mm, of Hg), and of the oxygen 


ANIMAL HEAT. 


105 


in the venous blood (22 mm. Hg), and of the difference of the carbonic 
acid tension in the venous blood (41 mm. Hg), and in the air cells (27 mm. 
Hg), it might be concluded that the passage of the gases might be due 
solely to pressure. The absorption of oxygen, however, does not follow 
absolutely the law of pressures; that chemical processes are involved is 
shown by the union of oxygen with the hemoglobin of the blood corpuscles. 
The exhalation of C0 2 is also partly a chemical process, as it has been 
shown that the quantity excreted is greatly increased when oxygen is simul¬ 
taneously absorbed. Oxygen not only favors the exhalation of loosely 
combined C0 2 , but favors the expulsion of that which can only be excreted 
by the addition of acids to the blood. 

Changes in the Blood during Respiration. 

As the blood passes through the lungs it is changed in color , from the 
dark purple hue of venous blood to the bright red scarlet of arterial 
blood. 

The heterogeneous composition of venous blood is exchanged for the 
uniform composition of the arterial. 

It gains oxygen and loses carbonic acid. 

Its coagulability is increased. Temperature is diminished. 

Asphyxia.—If the supply of oxygen to the lungs be diminished and 
the carbonic acid retained in the blood, the normal respiratory movements 
cease, the condition of asphyxia ensues, which soon terminates in death. 

The phenomena of asphyxia are, violent spasmodic action of the respi¬ 
ratory muscles, attended by convulsions of the muscles of the extremities, 
engorgement of the venous system, lividity of the skin, abolition of sensi¬ 
bility and reflex action, and death. 

The cause of death is a paralysis of the heart, from over distention by 
blood. The passage of the blood through the capillaries is prevented by 
contraction of the smaller arteries, from irritation of the vasomotor center. 
The heart is enfeebled by a want of oxygen and inhibited in its action by 
the inhibitory centers. 


ANIMAL HEAT. 

The Functional Activity of all the organs and tissues of the body is 
attended by the evolution of heat, which is independent, for the most part, 
of external conditions. Heat is a necessary condition for the due perform¬ 
ance of all vital actions; though the body constantly loses heat by radia¬ 
tion and evaporation , it possesses the capability of renewing it and main* 
H 




106 


HUMAN PHYSIOLOGY. 


taining it at a fixed standard. The normal temperature of the body in the 
adult, as shown by means of a delicate thermometer placed in the axilla, 
ranges from 97.25 0 Fahr. to 99.5 0 Fahr., though the mean normal tem¬ 
perature is estimated by Wunderlich at 98.6° Fahr. 

The temperature varies in different portions of the body, according to 
the degree in which oxidation takes place; being the highest in the muscles 
during exercise, in the brain, blood, liver, etc. 

The Conditions which Produce Variations in the normal tempera¬ 
ture of the body are : age, period of the day, exercise, food and drink, 
climate, season, and disease. 

Age .—At birth the temperature of the infant is about 1° F. above that of 
.the adult, but in a few hours falls to 95.5 0 F., to be followed in the course 
of 24 hours by a rise to the normal or a degree beyond. During childhood 
the temperature approaches that of the adult; in aged persons the tempera¬ 
ture remains about the same, though they are not as capable of resisting 
the depressing effects of external cold as adults. A diurnal variation of 
the temperature occurs from i.8° F. to 3.6° F. (Jurgensen) ; the maximum 
occurring late in the afternoon, from 4 to 9 P. M., the minimum , early in 
the morning, from 1 to 7 A. M. 

Exercise. —The temperature is raised from i° to 2° F. during active 
contractions of the muscular masses, and is probably due to the increased 
activity of chemical changes; a rise beyond this point being prevented by 
its diffusion to the surface, consequent on a more rapid circulation, radia¬ 
tion, more rapid breathing, etc. 

Food and Drink. —The ingestion of a hearty meal increases the tempera¬ 
ture but slightly; an absence of food, as in starvation, produces a marked 
decrease. Alcoholic drinks, in large amounts, in persons unaccustomed to 
their use, cause a depression of the temperature, amounting from i° to 2° 
F. Tea causes a slight elevation. 

External Tetnperature.— Long-continued exposure to cold, especially if 
the body is at rest, diminishes the temperature from i° to 2° F., while 
exposure to a great heat slightly increases it. 

Disease frequently causes a marked variation in the normal temperature 
of the body, rising as high as 107° F. in typhoid fever, and 105° F. in 
pneumonia; in cholera it falls as low as 8o° F. Death usually occurs 
when the heat remains high and persistent, from 106° to lio°F.; the 
increase of heat in disease is due to excessive production rather than to 
diminished elimination. 

The Source of Heat is to be sought for in the chemical decompositions 


ANIMAL HEAT. 


107 


and hydrations taking place during the general process of nutrition, and the 
combustion of the carbonaceous compounds by the oxygen of the inspired 
air; the amount of its production is in proportion to the activity of the in¬ 
ternal changes. 

Every contraction of a muscle, every act of secretion, each exhibition 
of nerve force, is accompanied by a change in the chemical composition of 
the tissues and an evolution of heat. The reduction of the disintegrated 
tissues to their simplest form by oxidation, the combination of the oxygen 
of the inspired air with the carbon and hydrogen of the blood and tissues, 
results in the formation of carbonic acid and water and the generation of a 
large amount of heat. 

Certain elements oC the food, particularly the non-nitrogenized sub¬ 
stances, undergo oxidation without taking part in the formation of the 
tissues, being transformed into carbonic acid and water, and thus increase 
the sum of heat in the body. 

Heat-producing Tissues.—All the tissues of the body add to the 
general amount of heat, according to the degree of their activity. But 
special structures, on account of their mass and the large amount of 
blood they receive, are particularly to be regarded as heat producers; 
e. g. 

1. During mental activity the brain receives nearly one-fifth of the entire 
volume of blood, and the venous blood returning from it is charged with 
waste matters, and its temperature is increased. 

2. The muscular tissue , on account of the many chemical changes occur¬ 
ring during active contractions, must be regarded as the chief heat- 
producing tissue. 

3. The secreting glands , during their functional activity, add largely to 
the amount of heat. 

The entire quantity of heat generated within the body has been demon¬ 
strated experimentally to be about 2300 calories, a calorie or heat unit 
being that amount of heat required to raise the temperature of one kilo, of 
water (2.2 lbs.) one degree Centigrade. This quantity of heat, if not utilized 
and retained within the body, would elevate its temperature in 24 hours 
about 6o° F. That this volume of heat depends very largely upon the 
oxidation of the food stuffs can be shown experimentally. 

The normal temperature of the body is maintained by a constant expen¬ 
diture of the heat in several directions :— 

1. In warming the food, drink, and air that are consumed in 24 hours. 
For this purpose about 157 heat units are required. 


108 


HUMAN PHYSIOLOGY. 


2. In evaporating water from the skin and lungs; 619 heat units being 
utilized for this purpose. 

3. In radiation and conduction. By these processes the body loses at 
least 50 per cent, of its heat, or 1156 heat units. 

4. In the production of work; the work of the circulatory, respiratory, 
muscular, and nervous apparatus being performed by the transformation of 
369 heat units into units of work. 

The nervous system influences the production of heat in a part by 
increasing the amount of blood going through it by its action upon the 
vasomotor nerves. Whether there exists a special heat center has not 
been satisfactorily determined, though this is probable. 


SECRETION. 


The Process of Secretion consists in the separation of materials from 
the blood which are either to be again utilized to fulfil some special pur¬ 
pose in the economy or are to be removed from the body as excrementi- 
tious matter; in the former case they constitute the secretions , in the latter, 
the excretions. 

The materials which enter into the composition of the secretions are 
derived from the nutritive principles of the blood, and require special 
organs, e. g ., gastric glands, mammary glands, etc. for their proper 
elaboration. 

The materials which compose the excretions preexist in the blood, and 
are the results of the activities of the nutritive process; if retained within 
the body they exert a deleterious influence upon the composition of the 
blood. 

Destruction of a secreting gland abolishes the secretion peculiar to it, 
and it cannot be formed by any other gland; but among the excreting 
organs their exists a complementary relation, so that if the function of one 
organ be interfered with, another performs it to a certain extent. 


CLASSIFICATION OF THE SECRETIONS. 


PERMANENT FLUIDS. 


Serous fluids. 

Synovial fluid. 

Aqueous humor of the eye. 


Vitreous humor of the eye. 

Fluid of the labyrinth of the internal 


ear. 

Cerebro-spinal fluid. 


SECRETIONS. 


109 


TRANSITORY FLUIDS. 


Mucus. 

Sebaceous matter. 

Cerumen (external meatus). 
Meibomian fluid. 

Milk and colostrum. 

Tears. 

Saliva. 


Gastric juice. 

Pancreatic juice. 

Secretion from Brunner s glands. 
Secretion from Leiberkiihn’s glands. 
Secretions from follicles of the large 


intestine. 

Bile (also an excretion). 


EXCRETIONS. 


Perspiration and the secretion of 
the axillary glands. 


Urine. 

Bile (also a secretion). 


FLUIDS CONTAINING FORMED ANATOMICAL ELEMENTS. 


Seminal fluid, containing spermatozoids. Fluid of the Graafian follicles. 

The Essential Apparatus for secretion is a delicate, homogeneous, 
structureless membrane, on one side of which, in close contact, is a capil¬ 
lary plexus of blood-vessels, and on the other side a layer of cells whose 
physiological function varies in different situations. 

Secreting organs may be divided into membranes and glands. 

Serous membranes usually exist as closed sacs, the inner surface of wdiich 
is covered by pale, nucleated epithelium, containing a small amount of 
secretion. 

The serous membranes are the pleura,peritoneum,pericardium, synovial 
sacs, etc. 

The serous fluids are of a pale amber color, somewhat viscid, alkaline, 
coagulable by heat, and resemble the serum of the blood ; their amount 
is but small; the pleural varies from 4 to 7 drams; the peritoneal from 
1 to 4 ounces; the pericardial from 1 to 3 drams. 

The synovial fluid is colorless, alkaline, and extremely viscid, from the 
presence of synovin. 

The function of serous fluids is to moisten the opposing surfaces, so as to 
prevent friction during the play of the viscera. 

The mucous membranes are soft and velvety in character, and line the 
cavities and passages leading to the exterior of the body, e.g., the gastro¬ 
intestinal, pulmonary, and genito-urinary. They consist of a primary 
basement membrane covered with epithelial cells, which in some situations 
are tessellated, in others, columnar. 

Mucus is a pale, semi-transparent, alkaline fluid, containing epithelial 
cells and leucocytes. It is composed, chemically, of water, an albuminous 


110 


HUMAN PHYSIOLOGY. 


principle, mucosin, and mineral salts; the principal varieties are nasal, 
bronchial, vaginal, and urinary. 

Secreting Glands are formed of the same elements as the secreting 
membranes; but instead of presenting flat surfaces, are involuted, forming 
tubules, which may be simple follicles, eg ., mucous, uterine, or intestinal; 
or compound follicles, e. g., gastric glands, mammary glands ; ox racemose 
glands, e.g., salivary glands and pancreas. They are composed of a base¬ 
ment membrane, enveloped by a plexus of blood-vessels, and are lined by 
epithelial and true secreting cells , which in different glands possess the 
capability of elaborating elements characteristic of their secretions. 

In the Production of the Secretion two essentially different processes 
are concerned :— 

1. Chemical. —The formation and elaboration of the characteristic 
organic ingredients of the secreted fluids, e.g., pepsin, pancreatin, takes 
place during the intervals of glandular activity, as a part of the general 
function of nutrition. They are formed by the cells lining the glands, 
and can often be seen in their interior with the aid of the microscope, eg., 
bile in the liver cells, fat in the cells of the mammary gland. 

2. Physical .—Consisting of a transudation of water and mineral salts 
from the blood into the interior of the gland. 

During the intervals of glandular activity, only that amount of blood 
passes through the gland sufficient for proper nutrition ; when the gland 
begins to secrete, under the influence of an appropriate stimulus, the blood¬ 
vessels dilate and the quantity of blood becomes greatly increased beyond 
that flowing through the gland during its repose. 

Under these Conditions a transudation of water and salt takes place, 
washing out the characteristic ingredients, which are discharged by the 
gland ducts. The discharge of the secretions is intermittent; they are 
retained in the glands until they receive the appropriate stimulus, when 
they pass into the larger ducts by the vis-a-tergo, and are then discharged 
by the contraction of the muscular walls of the ducts. 

The activity of glandular secretion is hastened by an increase in the 
blood pressure and retarded by a diminution. 

The nervous centers in the medulla oblongata influence secretion, (i) by 
increasing or diminishing the amount of blood entering a gland; (2) by 
exerting a direct influence upon the secreting cells themselves, the centers 
being excited by reflex irritation, mental emotion, etc. 


mammary glands. 


ill 


MAMMARY GLANDS. 

The Mammary Glands secrete the milk, and undergo at different 
periods of life remarkable changes in structure. Though rudimentary in 
childhood, they gradually increase in size as the young female approaches 
puberty. 

The gland presents, at its convexity, a small prominence of skin, the 
nipple , surrounded by an areola of a deeper tint. It is covered anteriorly 
by a layer of adipose tissue and posteriorly by a fibrous structure which 
attaches it loosely to the pectoralis muscle. 

During utero-gestation the mammae become large, firm, well-developed, 
and lobulated ; the areola becomes darker and the veins more prominent. 
In the intervals of lactation the glands gradually sink in size to their 
original condition, undergo involution, and become non-secreting organs. 

Structure of the Mammae.—The mamma is a conglomerate gland, 
consisting of a number of lobes, from 15 to 20 in number, each of which 

subdivided into lobules made up of gland vesicles or acini. The ducts 
w'hich convey the secretion to the exterior, the lactiferous ducts , open by 
15 to 20 orifices upon the surface of the nipple, at the base of which they 
are dilated to form little reservoirs in which the milk collects during the 
periods of active secretion. 

The walls of the lacteal duct consist of white, fibrous tissue, and non- 
striated muscular fibers, lined by short columnar cells, which disappear 
during- active lactation. The ducts measure about the T2 of an inch in 
diameter; as they pass into the substance of the gland each duct divides 
into a number of branches, which are distributed to distinct lobules and 
terminate in the acini. 

An acinus is made up of a number of vesicles composed of a homoge¬ 
neous membrane, lined by pavement epithelium. The gland vesicles are 
held together by white, fibrous tissue, which unites the lobules into lobes. 


MILK. 

Milk has a pale blue color, is almost inodorous, of a sweetish taste, an 
alkaline reaction, and a specific gravity varying from 1.025 to 1.046. 
Examined microscopically, it is seen to contain an immense number of 
globules, measuring the °f an * n diameter, suspended in a clear 

fluid; these are the milk globules , formed of a small mass of oily matter 
covered by a layer of albumin. 


112 


HUMAN PHYSIOLOGY. 


The quantity of milk secreted by the human female in 24 hours, during 
the period of lactation, is about two to three pints; the quantity removed by 
the infant from a full breast at one time being about two ounces. 

COMPOSITION OF MILK. 


Water. 890.00 

Proteids, including casein and serum albumin, . . . 35 -°° 

Fatty matter (butter),. 25.00 

Sugar (lactose) with extractives, .. 48.00 

Salts,. 2.00 


1000.00 

Casein is the nutritive principle of milk, and constitutes its most important 
ingredient. It is held in solution by an alkali, but upon the addition of an 
acid it undergoes coagulation, passing into a semi-solid form. The presence 
of lactic acid, resulting from a transformation of milk sugar, causes spon¬ 
taneous coagulation to take place. 

The fatty matter is more or less solid at ordinary temperature, and con¬ 
sists of margarin and olein; when subjected to the churning process the 
globules run together and form a coherent mass, the butter. 

When milk is allowed to stand for a varying length of time, the fat 
globules rise to the surface, forming a layer more or less thick, the cream. 

Milk sugar or lactose is an important ingredient in the food of the young 
'child; it is readily transformed into lactic acid in the presence of nitrogen- 
ized ferments. 

Influences Modifying the Secretion.—During lactation there is a 
demand for an increased amount of fluid, and if not supplied, the amount 
of milk secreted is diminished. Good food in sufficient quantity is neces¬ 
sary for the proper elaboration of milk, though no particular article influ¬ 
ences its production. 

Mental emotion at times influences the character of the milk, decreasing 
the amount of its different constituents. 

Mechanism of Secretion.—The water and salts preexist in the blood 
and pass into the gland vesicles by osmosis. The casein, fatty matter, and 
sugar appear only in the mammary gland, but the mechanism of their 
formation is not understood. 

Colostrum is a yellowish, opaque fluid, formed in the mammary glands 
toward the latter period of utero-gestation; it consists of water, albumin, 
fat, sugar, and salts, and acts as a laxative to the newly-born infant. 







113 


VASCULAR OR DUCTLESS GLANDS. 

VASCULAR OR DUCTLESS GLANDS. 

The Vascular Glands are regarded as possessing the power of acting 
upon certain elements of the food and aiding the process of sanguinifica- 
tion; of modifying the composition of the blood as it flows through their 
substance, by some act of secretion. 

The vascular glands are the spleen , supra-renal capsules , thyroid and 
thyvms glands. 

The Spleen is about 5 inches in length, 6 ounces in weight, of a dark- 
bluish color, and situated in the left hypochondriac region. It is covered 
externally by a reflection of the peritoneum, beneath which is the proper 
fibrous coat, composed of areolar and elastic tissue and non-striated muscu¬ 
lar fibers. From the inner surface of the fibrous envelope processes or tra¬ 
beculae are given off, which penetrate the substance of the gland, forming a 
network, in the meshes of which is contained the spleen pulp. The splenic 
artery divides into a number of branches, some of which, when they become 
very minute, pass directly into veins, while others terminate in true capil¬ 
laries. 

As the capillary vessels ramify through the substance of the gland, their 
walls frequently disappear and the blood passes from the arteries into the 
veins through lacunce (Gray). 

The splenic or Malpighian corpuscles are small bodies, spherical or 
ovoid in shape, the ^ of an inch in diameter, situated upon the sheaths of 
the small arteries. They consist of a delicate membrane containing a 
semi-fluid substance composed of numerous small cells resembling lymph 
corpuscles. The spleen pulp is a dark-red, semi-fluid substance, of a soft 
consistence, contained in the meshes of the trabeculae. In it are found 
numerous corpuscles, like those observed in the Malpighian bodies, blood 
corpuscles in a natural and altered condition, nuclei, and pigment 
granules. 

Function of the Spleen.—Probably influences the preparation of the 
albuminous food for nutrition; during digestion the spleen becomes larger, 
its contents are increased in amount, and after digestion it gradually dimin¬ 
ishes in size, returning to the normal condition. 

The red corpuscles are here disintegrated, after having fulfilled their 
unction in the blood, the splenic venous blood containing relatively a 
small quantity. 

The white corpuscles appear to be increased in number, the blood of the 
splenic vein containing an unusually large proportion. 


114 


HUMAN PHYSIOLOGY. 


The spleen serves also as a reservoir for blood when the portal circula¬ 
tion becomes obstructed. 

The newous system controls the enlargement of the spleen ; division of 
the nerve produces dilatation of the vessels, stimulation contracts them. 

The Suprarenal Capsules are triangular, flattened bodies, situated 
above the kidney. They are invested by a fibrous capsule sending in 
trabeculae, forming the framework. The glandular tissue is composed of 
two portions, a cortical and medullary. The cortical being made up of 
small cylinders lined by cells and containing an opaque mass, nuclei, and 
granular matter. The medullary consists of a fibrous network containing 
in the alveoli nucleated protoplasm. 

The Thyroid Gland consists of a fibrous stroma, containing ovoid 
closed sacs, measuring on the average ITT of an inch, formed of a delicate 
membrane lined by cells; the contents of the sacs consist of yellowish 
albuminous fluid. 

The Thymus Gland is most developed in early life and almost disap¬ 
pears in the adult. It is divided by processes of fibrous tissue into lobules, 
and these again into follicles which contain lymphoid corpuscles. 

The functions of the vascular organs appear to be the more complete 
elaboration of the blood necessary for proper nutrition ; they are most highly 
developed during infancy and embryonic life, when growth and develop¬ 
ment are most active. 


EXCRETION. 

The Principal Excrementitious Fluids discharged from the body 
are the urine, perspiration, and bile; they hold in solution principles of 
waste w'hich are generated during the activity of the nutritive process, and 
are the ultimate forms to which the organic constituents are reduced in the 
body. They also contain inorganic salts. 

The Urinary Apparatus consists of the kidneys, ureters, and bladder. 


KIDNEYS. 

The Kidneys are the organs for the secretion of urine; they resemble 
a bean in shape, are from four to five inches in length, two in breadth, and 
weigh from four to six ounces. 

They are situated in the lumbar region, one on each side of the vertebral 


KIDNEYS. 115 

column, behind the peritoneum, and extend from the nth rib to the crest 
of the ilium; the anterior surface is convex, the posterior surface concave, 
the latter presenting a deep notch, the hilus. 

The kidney is surrounded by a thin, smooth membrane composed of 


Fig. 13. 



LONGITUDINAL SECTION THROUGH THE KIDNEY, THE PELVIS OF THE KIDNEY, AND A 
. NUMBER OF RENAL CALYCES. 

A, branch of the renal artery; U, ureter; C, renal calyx ; 1, cortex; 1', medullary 
rays ; 1", labyrinth, or cortex proper; 2, medulla; 2', papillary portion of medulla, 
or medulla proper; 2", border layer of the medulla; 3, 3, transverse section through 
the axes of the tubules of the border layer; 4, fat of the renal sinus ; 5, 5, arterial 

branches; *, transversely coursing medulla rays.— Tyson, after Henle. 









116 


HUMAN PHYSIOLOGY. 


white fibrous and yellow elastic tissue ; though it is attached to the surface 
of the kidney by minute processes of connective tissue, it can be readily torn 
away. The substance of the kidney is dense but friable. 

Upon making a longitudinal section of the kidney it will be observed 
that the hilus extends into the interior of the organ and expands to form 
a cavity known as the sinus. This cavity is occupied by the upper 
dilated portion of the ureter, the interior of which forms, the pelvis. The 
ureter subdivides into several portions, which ultimately give origin to a 
number of smaller tubes termed calyces , which receive the apices of the 
pyramids. 

The Parenchyma of the Kidney consists of two portions, viz.:— 
i. An internal or medullary portion, consisting of a series of pyramids 
or cones , some twelve or fifteen in number. They 
Fig. 14. present a distinctly striated appearance, a condition 

due to the straight direction of the tubules and blood¬ 
vessels. 

2. An external or cortical portion, consisting of a 
delicate matrix containing an immense number of 
tubules having a markedly convoluted appearance. 
Throughout its structure are found numerous small 
ovoid bodies termed Malpighian corpuscles. 

The Uriniferous Tubules.—The kidney is a 
compound tubular gland composed of microscopic 
tubules, whose function it is to secrete from the 
blood those waste products which collectively con¬ 
stitute the urine. If the apex of each pyramid be 
examined .with a lens, it will present a number of 
small orifices which are the beginnings of the uri¬ 
niferous tubules. From this point the tubules pass 
outward in a straight but somewhat diverging man¬ 
ner toward the cortex, giving off at acute angles a 
number of branches (Fig. 14). From the apex to 
D tf?” a the Sod the base of the Py famid s they are known as the 

in which the urinife- tubules of Bellini. In the cortical portion of the 

rous tubes unite to , , , . , 

form primitive cones, kidney each tubule becomes enlarged and twisted, 

— Tyson , after Lud- an( j a f ter p ursu j ng an extremely convoluted course, 

turns backward into the medullary portion for some 

distance, forming the descending limb of Henle’s loop; it then turns 

upon itself, forming the ascending limb of the loop, reenters the cortex, 




















KIDNEYS. 


117 


again expands, and finally terminates in a spherical enlargement known 
as Milller's or Bowman's capsule. Within this capsule is contained a 
small tuft of blood-vessels constituting the glo?nerulus or Malpighian cor¬ 
puscle. 

Structure of the Tubules.—Each tubule consists of a basement mem¬ 
brane lined by epithelial cells throughout its entire extent. The tubule 
and its contained epithelium vary in shape and size in different parts of 
its course. The termination of the convoluted tube consists of a little sac 
or capsule, which is ovoidal in shape and measures about of an inch 
in size. This capsule is lined by a layer of flattened epithelial cells which 
is also reflected over the surface of the glomerulus. During the periods 
of secretory activity, the blood-vessels of the glomerulus become filled 
with blood, so that the cavity of the sac is almost obliterated; after secre¬ 
tory activity the blood-vessels contract and the sac cavity becomes enlarged. 
In that portion of the tubule lying between the capsule and Henle’s loop 
the epithelial cells are cuboidal in shape; in Henle’s loop they are flat¬ 
tened, while in the remainder of the tubule they are cuboidal and 
columnar. 

Blood-Vessels of the Kidney.— The renal artery is of large size and 
enters the organ at the hilum ; it divides into several large branches, which 
penetrate the substance of the kidney, between the pyramids, at the base 
of which they form an anastomosing plexus, which completely surrounds 
them. From this plexus vessels follow the straight tubes toward the apex, 
while others, entering the cortical portion, divide into small twigs, which 
enter the Malpighian body and form a mass of convoluted vessels, the 
glomerulus. After circulating through the Malpighian tuft, the blood is 
gathered together by two or three small veins, which again subdivide and 
form a fine capillary plexus, which envelops the convoluted tubules; from 
this plexus the veins converge to form the emulgent vein, which empties 
into the vena cava. 

The Nerves of the Kidney follow the course of the blood-vessels and 
are derived from the renal plexus. 

The Ureter is a membranous tube, situated behind the peritoneum, 
about the diameter of a goose-quill, 18 inches in length, and extends from 
the pelvis of the kidney to the base of the bladder, which it perforates in 
an oblique direction. It is composed of three coats, fibrous, muscular and 
mucous. 

The Bladder is a reservoir for the temporary reception of the urine 
prior to its expulsion from the body; when fully distended it is ovoid in 


118 


HUMAN PHYSIOLOGY. 


shape, and holds about one pint. It is composed of four coats,: serous , 
muscular , the fibers of which are arranged longitudinally and circularly, 
areolar , and mucous. The orifice of the bladder is controlled by the 
sphincter vesicce , a muscular band about half an inch in width. 

As soon as the Urine is Formed it passes through the tubuli uriniferi 
into the pelvis, and from thence through the ureters into the bladder, which 
it enters at an irregular rate. Shortly after a meal, after the ingestion of 
large quantities of fluid, and after exercise, the urine flows into the bladder 
quite rapidly, while it is reduced to a few drops during the intervals of di¬ 
gestion. It is prevented from regurgitating into the ureters on account of the 
oblique direction they take between the mucous and muscular coats. 

Nervous Mechanism of Urination.—When the urine has passed into 
the bladder, it is there retained by the sphincter vesicae muscle, kept in a 
state of tonic contraction by the action of a nerve center in the lumbar 
region of the spinal cord. This center can be inhibited and the sphincter 
relaxed, either reflexly , by impressions coming through sensory nerves from 
the mucous membrane of the bladder, or directly, by a voluntary impulse 
descending the spinal cord. When the desire to urinate is experienced, 
impressions made upon the vesical sensory nerves are carried to the centers 
governing the sphincter and detrusor urince muscles and to the brain. If 
now the act of urination is to take place, a voluntary impulse originating 
in the brain passes down the spinal cord, and still further inhibits the 
sphincter vesicae center, with the effect of relaxing the muscle, and of 
stimulating the center governing the detrusor muscle, with the effect of con¬ 
tracting the muscle and expelling the urine. If the act is to be suppressed, 
voluntary impulses inhibit the detrusor center and possibly stimulate the 
sphincter center. 

The genito-spinal center controlling these movements is situated in that 
portion of the spinal cord corresponding to the origin of the 3d, 4th and 
5th sacral nerves. 


URINE. 

Normal urine is of a pale yellow or amber color, perfectly transparent, 
with an aromatic odor, an acid reaction, a specific gravity of 1.020, and a 
temperature when first discharged of ioo° Fahr. 

The color varies considerably in health, from a pale yellow to a brown hue 
due to the presence of the coloring matter, urobilin or urochrome. 


URINE. H9 

The transparency is diminished by the presence of mucus, the calcium 
and magnesium phosphates, and the mixed urates. 

The reaction of the urine is acid, owing to the presence of acid phosphate 
of sodium. The degree of acidity, however, varies at different periods of 
the day. Urine passed in the morning is strongly acid, while that passed 
during and after digestion, especially if the food is largely vegetable in 
character, is either neutral or alkaline. 

The specific gravity varies from 1.015 to 1.025. 

The quantity of urine excreted in 24 hours is between 40 and 50 fluid 
ounces, but ranges above and below this standard. 

The odor is characteristic, and caused by the presence of taurylic and 
phenylic acids, but is influenced by vegetable foods and other substances 
eliminated by the kidneys. 


COMPOSITION OF URINE. 


Water,. 

Urea,. 

Other nitrogenized crystalline bodies, uric acid, prin¬ 
cipally in the form of alkaline urates, 

Creatin, creatinin, xanthin, hypoxanthin, 

Hippuric acid, leucin, tyrosin, taurin, cystin, all in 
small amounts, and not constant, 

Mucus and pigment, 

Salts:— 

Inorganic: principally sodium and potassium sul¬ 
phates, phosphates, and chlorids, with magnesium 
and calcium phosphates, traces of silicates and 
chlorids, 

Organic: lactates, hippurates, acetates, formates, 
which appear only occasionally, 

Sugar,. 

Gases (nitrogen and carbonic acid principally). 


967. 

14.230 

10.635 


8.135 


a trace. 


1000.00 


The Average Quantity of the principal constituents excreted in 24 
hours is as follows :— 


Water,. 52 fluid oz. 

Urea.512.4 grains. 

Uric acid,. . . 8.5 “ 

Phosphoric acid,.45 0 “ 

Sulphuric acid,. 31.H “ 

Inorganic salts,.. 323.25 “ 

Lime and magnesia,. 6.5 “ 
















120 


HUMAN PHYSIOLOGY. 


To Determine the Amount of solid matters in any given amount of 
urine, multiply the last two figures of the specific gravity by the coefficient 
of Hteser, 2.33; e. g., in 1000 grains of urine having a specific gravity 
1.022, there are contained 22 X 2 -33 = 5 r - 2 6 grains of solid matter. 

Organic Constituents of Urine.—Urea is one of the most important 
of the organic constituents of the urine, and is present to the extent of from 
2.5 to 3.2 per cent. Urea is a colorless, neutral substance, crystallizing to 
four-sided prisms terminated by oblique surfaces. When crystallization is 
caused to take place rapidly, the crystals take the form of long, silky 
needles. Urea is soluble in water and alcohol ; when subjected to pro¬ 
longed boiling it is decomposed, giving rise to carbonate of ammonia. In 
the alkaline fermentation of urine, urea takes up two molecules of water 
with the production of carbonate of ammonia. 

The average amount of urea excreted daily has been estimated at about 
500 grains. As urea is one of the principal products of the breaking up of 
the albuminous compounds within the body, it is quite evident that the 
quantity produced and eliminated in 24 hours will be increased by any 
increase in the amount of albuminous food consumed, by a rapid destruc¬ 
tion of albuminous tissues, as is witnessed in various pathological states, in¬ 
anition, febrile conditions, fevers, etc. A farinaceous or vegetable diet will 
diminish the urea production nearly one-half. 

Muscular exercise when the nutrition of the body is in a state of equi¬ 
librium does not seem to increase the quantity of urea. 

Seat of Urea Formation.—As to the seat of urea formation, little 
is positively known. It is quite Certain that it preexists in the blood and is 
merely excreted by the kidneys. It is not produced in muscles, as even 
after prolonged exercise hardly a trace of urea is to be found in them. 
Experimental and pathological facts point to the liver as the probable 
organ engaged in urea formation. Acute yellow atrophy of the liver, sup¬ 
purative diseases of the liver, diminish almost entirely the production of 
urea. 

Uric acid is also a constant ingredient of the urine and is closely allied 
to urea. It is a nitrogenized substance, carrying out of the body a large 
quantity of nitrogen. The amount eliminated daily varies from 5 to 10 
grains. Uric acid is a colorless crystal belonging to the rhombic system. 
It is insoluble m water, and if eliminated in excessive amounts it is de¬ 
posited as a “ brick red ” sediment in the urine. It is doubtful if uric acid 
exists in a free state, being combined for the most part with sodium and 
potassium bases forming urates. It is to be regarded as one of the termi- 


URINE. 


121 


nal products of the disas^imilation of albuminous compounds, and is prob¬ 
ably produced in the liver. 

Hippuric acid is found very generally in urine, though it is present 
only in small amounts. It is increased by a diet of asparagus, cranberries 
plums, and by the administration of benzoic and cinnamic acids. It is 
probably formed in the kidney. 

Kreatinin resembles the kreatin derived from muscles. It is a colorless 
crystal, belonging to the rhombic system. Its origin is unknown, though it 
is largely increased in amount by albuminous food. About 15 grains are 
excreted daily. 

Xanthin, Sarkin, Oxaluric Acid, and Allantoin are also constituents 
of urine. They are nitrogenized compounds and are also terminal products 
of albuminous compounds. 

Urobilin, the coloring matter of the urine, is a derivative of the bile pig¬ 
ments. It is particularly abundant in febrile conditions, giving to the urine 
its reddish-yellow color. 

Inorganic Constituents of Urine.—Earthy Phosphate. Phos¬ 
phoric acid in combination with magnesium and calcium is excreted daily 
to the extent of from 15 to 30 grains. The phosphates are insoluble in 
water, but are held in solution in the urine by its acid ingredients, alkalinity 
of the urine being attended with a copious precipitation of the phosphates. 
Mental work increases the amount of phosphoric acid excreted, a condition 
caused by increased metabolism of the nervous tissue. 

Sulphuric acid in combination with sodium and potassium constitute the 
sulphates, of which about 30 grains are excreted daily. Sulphuric acid 
results largely from the decomposition of albuminous food and from in¬ 
creased destruction of animal tissues. 

The Gases of the urine are carbonic acid and nitrogen. 

Mechanism of Urinary Secretion.—As the kidney anatomically pre¬ 
sents an apparatus for filtration (the Malpighian bodies), and an apparatus 
for secretion (the epithelial cells of the urinary tubules), it might be inferred 
that the elimination of the constituents of the urine is accomplished by the 
twofold process of filtration and secretion ; that the water and highly 
diffusible inorganic salts simply pass by diffusion through the walls of the 
blood-vessels of the glomerulus into the capsule of Muller, while the urea 
and remaining organic constituents are removed by true secretory action of 
the renal epithelium. Modern experimentation supports this view of renal 
action. 


1 


122 


HUMAN PHYSIOLOGY. 


The secretion of urine is therefore partly physical and partly vital. 

The filtration of urinary constituents from the'glomerulus into Muller’s 
capsule depends largely upon the blood pressure and the rapidity of blood 
flow in the renal artery and glomerulus. Among the influences which 
increase the pressure and velocity, may be mentioned increased frequency 
and force of the heart’s action, contraction of the capillary vessels of the 
body generally, dilatation of the renal artery, increase in the volume of the 
blood. 

The reverse conditions lower the blood pressure and diminish the secre¬ 
tion of urine. • 

The elimination of the organic matters by secretory activity of the renal 
epithelium seems to be well established by modern experiments. These 
substances, removed from the blood in the secondary capillary plexus of 
blood-vessels, by a true selective action of the epithelium, are dissolved and 
washed toward the pelves by the liquid coming from the capsules. 

The blood supply to the kidney is regulated by the nervous system. If 
the renal nerves be divided, the renal artery dilates and a copious flow of 
urine takes place. If the peripheral ends of the same nerves be stimulated 
the artery contracts and the urinary flow ceases. The same is true of the 
splanchnic nerves, through which the vasomotor nerves coming from the 
medulla oblongata and spinal cord pass to the renal plexus. 


LIVER. 

The Liver is a highly vascular, conglomerate gland, appended to the 
alimentary canal. It is the largest gland in the body, weighing about 4^ 
pounds; it is situated in the right hypochondriac region, and retained in 
position by five ligaments, four of which are formed by duplicatures of the 
peritoneal investment. 

The proper coat of the liver is a thin but firm fibrous membrane, closely 
adherent to the surface of the organ, which it penetrates at the transverse 
fissure, and follows the vessels in their ramifications through its substance, 
constituting Glisson's capsule. 

Structure of the Liver.—The liver is made up of a large number of 
small bodies, the lobules , rounded or ovoid in shnpe, measuring the fa of 
an inch in diameter, separated by a space in which are situated blood¬ 
vessels, nerves, hepatic ducts, and lymphatics. 

The Lobules are composed of cells, which, when examined microscopi¬ 
cally, exhibit a rounded or polygonal shape, and measure, on the average, 
tlie ToW of an inc h in diameter; they possess one, and at times two, nuclei; 


LIVER. 


123 


they also contain globules of fat, pigment matter, and animal starch. The 
cells constitute the secreting structure of the liver, and are the true hepatic 

cells. 

The Blood-vessels which enter the liver are (i) The portal vein, 
made up of the gastric, splenic , superior and inferior mesenteric veins', (2) 
the hepatic artery, a branch of the celiac axis; both of which are invested 
by a sheath of areolar tissue; the vessels which leave the liver are the 
hepatic veins , originating in its interior, collecting the blood distributed by 
the portal vein and hepatic artery, and conducting it to the ascending vena 
cava. 

Distribution of Vessels.—The portal vein and hepatic artery , upon 
entering the liver, penetrate its substance, divide into smaller and smaller 
branches, occupy the spaces between the lobules, completely surrounding 
and limiting them, and constitute the interlobular vessels. The hepatic 
artery, in its course, gives off branches to the walls of the portal vein and 
Glisson’s capsule, and finally empties into the small branches of. the portal 
vein in the interlobular spaces. 

The interlobular vessels form a rich plexus around the lobules, from 
which branches pass to neighboring lobules and enter their substance, 
where they form a very fine network of capillary vessels, ramifying over 
the hepatic cells, in which the various functions of the liver are performed. 
The blood is then collected by small veins, converging toward the center 
of the lobule, to form the intralobular vein, which runs through its long 
axis and empties into the sub-lobular vein. The hepatic veins are formed 
by the union of the sub-lobular veins, and carry the blood to the ascending 
vena cava; their walls are thin and adherent to the substance of the 
hepatic tissue. 

The Hepatic Ducts or Bile Capillaries originate within the lobules, 
in a very fine plexus lying between the hepatic cells; whether the smallest 
vessels have distinct membranous walls, or whether they originate in the 
spaces between the cells by open orifices, has not been satisfactorily deter¬ 
mined. 

The Bile Channels empty into the interlobular ducts, which measure 
about 20V0 an * n diameter, and are composed of a thin, homogeneous 
membrane lined by flattened epithelial cells. 

As the interlobular bile ducts unite to form larger trunks, they receive 
an external coat of fibrous tissue, which strengthens their walls; they finally 
unite to form one large duct, the hepatic duct , which joins the cystic duct; 
the union of the two forms the ductus communis choledochus , which is 


124 


HUMAN PHYSIOLOGY. 


about three inches in length, the size of a goose quill, and opens into the 
duodenum. 

The Gall Bladder is a pear-shaped sack, about four inches in length, 
situated in a fossa on the under surface of the liver. It is a reservoir for 
the bile, and is capable of holding about one ounce and a half of fluid. It 
is composed of three coats, (i) serous, a reflection of the peritoneum, (2) 
fibrous and muscular, (3) mucous. 

Functions of the Liver.—The liver is a complex organ having a 
variety of relations to the general processes of the body. While its physi¬ 
ological actions are not yet wholly understood, it may be said that it— 

1. Secretes bile. 

2. Forms glycogen. 

3. Assists in the formation of urea and allied products. 

4. Modifies the composition of the blood as it passes through it. 

The Secretion of Bile.—The characteristic constituents of the bile do 
not preexist in the blood, but are formed within the interior of the liver 
cells out of materials derived from the venous and arterial blood. The 
hepatic cells absorbing these materials elaborate them into bile elements, and 
in so doing undergo histological changes similar to those exhibited by other 
secretory glands. The bile once formed, it passes into the mouths of the 
bile capillaries, near the periphery of the lobules. Under the influence of the 
vis-a-tergo of the new-formed bile it flows from the smaller into the larger 
bile ducts, and finally empties into the intestine, or is regurgitated into the 
gall bladder, where it is stored up until it is required for the digestive pro¬ 
cess in the small intestine. The study of the secretion of bile by means of 
biliary fistulae reveals the facts that the secretion is continuous and not inter-, 
mittent ; that the hepatic cells are constantly pouring bile into the ducts, 
which convey it into the gall bladder. As this fluid is required only during 
intestinal digestion, it is only then that the walls of the gall bladder contract 
and discharge it into the intestine. 

The flow of bile from the liver cells into the gall bladder is accomplished 
by the inspiratory movements of the diaphragm, the contraction of the 
muscular fibers of the biliary ducts, as well as the vis-a-tergo of new- 
formed bile. Any obstacle to the outflow of bile into the intestine leads to 
an accumulation within the bile ducts. The pressure within the ducts in¬ 
creasing beyond that of the blood within the capillaries, a re-absorption of 
biliary matters by the lymphatics takes place, giving rise to the phenomena 
of jaundice. 

The Bile is both a secretion and an excretion ; it contains new constitu- 


LIVER. 


125 


ents which are formed only in the substance of the liver, and are destined 
to play an important part ultimately in nutrition; it contains also waste 
ingredients which are discharged into the intestinal canal and eliminated 
from the body. 

Glycogenic Function.—In addition to the preceding function, Bernard, 
in 1848, demonstrated the fact that the liver, during life, normally produces 
a sugar-forming substance, analogous in its chemical composition to starch, 
which he terms glycogen ; also that when the liver is removed from the 
body, and its blood-vessels thoroughly washed out, after a few hours sugar 
again makes it appearance in abundance. 

It can be shown to exist in the blood of the hepatic vein as well as in a 
decoction of the liver substance, by means of either Trommer’s or Fehling’s 
tests, even when the blood of the portal vein does not contain a trace of 
sugar. 

Origin and Destination of Glycogen.—Glycogen appears to be 
formed de novo in the liver cells, from materials derived from the food, 
whether the diet be animal or vegetable, though a larger per cent, is formed 
when the animal is fed on starchy and saccharin, than when fed on animal 
food. The glucose, which is one of the products of digestion, is absorbed 
by the blood-vessels, and carried directly into the liver; as it does not ap¬ 
pear in the urine, as it would if injected at once into the general circulation, 
it is probable that it is detained in the liver, dehydrated and stored up as 
glycogen. The change is shown by the following formula:— 

Glucose. Water. Glycogen. 

C 2 H 12 0 6 H 2 0 = C 6 H 10 O 5 

The glycogen thus formed is stored up in the hepatic cells for the future 
requirements of the system. When it is carried from the liver it is again 
transformed into glucose by the agency of a ferment. Glycogen does not 
undergo oxidation in the blood; this takes place in the tissues, particularly 
in the muscles, where it generates heat and contributes to the development 
of muscular force. 

Glycogen, when obtained from the liver, is an amorphous, starch-like 
substance, of a white color, tasteless and colorless, and soluble in water; by 
boiling with dilute acids, or subjected to the action of an animal ferment, 
it is easily converted into glucose. When an excess of sugar is generated 
by the liver, it can be found, not only in the blood of the hepatic vein, 
but also in other portions of the body; under these circumstances it is 
eliminated by the kidneys, appearing in the urine, constituting the condi¬ 
tion of glycosuria. 


126 


HUMAN PHYSIOLOGY. 


Formation of Urea.—The liver is now regarded by many physiologists 
to be the principal organ concerned in urea formation. The liver normally 
contains a certain amount of urea, and if blood be passed through the 
excised liver of an animal which has been in full digestion, a large amount 
of urea is obtained. The clinical evidence proves that in destructive dis¬ 
eases of the liver substance there is at once a falling off in urea elimination. 
Various drugs which increase liver action increase the urea in the urine. 

Elaboration of Blood.—Besides the capability of secreting bile, the 
liver possesses the property of. so acting upon and modifying the chemical 
composition of the products of digestion as they traverse its substance, 
that they readily assimilate with the blood, and are transformed into mate¬ 
rials capable of being converted into the elements of the blood and solid 
tissues. 

The albuminous particularly requires the modifying influence of the 
liver; for if it be removed from the portal vein and introduced into the 
jugular vein, it is at once removed from the blood by the action of the 
kidneys. 

The blood of the hepatic vein differs from the blood of the portal vein 
in being richer in blood corpuscles, both red and white; its plasma is more 
dense, containing a less percentage of water and a greater amount of solid 
constituents, but no fibrin; its serum contains less albumin, fats, and salts, 
but its sugar is increased. 

Influence of the Nervous System.—The nervous system directly 
controls the functional activity of the liver, and more especially its glyco¬ 
genic function. It was discovered by Bernard that puncture of the medulla 
oblongata is followed by such an enormous production of sugar that it is at 
once excreted by the kidneys, giving rise to diabetic or saccharin urine. 
This part of the medulla is, however, the vasomotor center for the blood¬ 
vessels of the liver. Destruction of this center, or injury to the vasomotor 
nerves emanating from it in any part of their course, is followed at once by 
dilatation of the hepatic blood-vessels, slowing of the blood current, a pro¬ 
found disturbance of the normal relation existing between the blood and 
liver cells, and a production of sugar. Many of the hepatic vasomotor 
nerves may be traced down the cord as far as the lumbar region, while 
others leave the cord high up in the neck and enter the cervical ganglia of 
the sympathetic and so reach the liver. Injury to the sympathetic ganglia 
is often followed by diabetes. Peripheral stimulation of various nerves, 
e. g ., sciatic, pneumogastric, depressor nerve, as well as the direct action of 
many drugs, impair or depress the hepatic vasomotor center and so give 
rise to diabetes. 


SKIN. 


127 


SKIN. 

The Skin, the external investment of the body, is a most complex and 
important structure, serving (i) as a protective covering; (2) an organ for 
tactile sensibility; (3) an organ for the elimination of excrementitious 
jnatters. 

The Amount of Skin investing the body of a man of average size is 
about twenty feet, and varies in thickness, in different situations, from the 
£ to the of an inch. 

The skin consists of two principal layers, viz., a deeper portion, the 
Coritwi , and a superficial portion, the Epidermis. 

The Corium, or Cutis Vera, may be subdivided into a reticulated and 
a papillary layer. The former is composed of white fibrous tissue, non- 
striated muscular fibers, and elastic tissue, interwoven in every direction, 
forming an areolar network, in the meshes of which are deposited masses 
of fat, and a structureless amorphous matter ; the latter is formed mainly of 
club-shaped elevations or projections of the amorphous matter, constituting 
the papillce ; they are most abundant, and well developed, upon the palms 
of the hands and the soles of the feet; they average the of an inch 
in length, and may be simple or compound ; they are well supplied with 
nerves, blood-vessels, and lymphatics. 

The Epidermis or Scarf Skin is an extra-vascular structure, a product 
of the true skin, and composed of several layers of cells. It may be 
divided into two layers, the rete mucosum or the Malpighian layer , and 
the horny or corneous. 

The former closely applies itself to the papillary layer of the true skin, 
and is composed of large, nucleated cells, the lowest layer of which, the 
“ prickle cells,” contain pigment granules, which give to the skin its varying 
tints in different individuals and in different races of men ; the more super¬ 
ficial cells are large, colorless, and semi-transparent. The latter , the corne¬ 
ous layer, is composed of flattened cells, which, from their exposure to the 
atmosphere, are hard and horny in texture ; it varies in thickness from 
of an inch on the palms of the hands and feet, to the of an inch in the 
external auditory canal. 

APPENDAGES OF THE SKIN. 

Hairs are found in almost all portions of the body, and can be divided 
into (i) long, soft hairs, on the head ; (2) short, stiff hairs, along the edges 
of the eyelids and nostrils; (3) soft, downy hairs, on the general cutaneous 


128 


HUMAN PHYSIOLOGY. 


surface. They consist of a root and a shaft, which is oval in shape, and 
about the ^ of an inch in diameter; it consists of fibrous tissue, covered 
externally by a layer of imbricated cells, and internally by cells containing 
granular and pigment material. 

The Root of the hair is embedded in the hair follicle, formed by a tubular 
depression of the skin, extending nearly through to the subcutaneous tissue; 
its walls are formed by the layers of the corium, covered by epidermic cells. 
At the bottom of the follicle is a papillary projection of amorphous matter, 
corresponding to a papilla of the true skin, containing blood-vessels and 
nerves, upon which the hair root rests. The investments of the hair roots 
are formed of epithelial cells, constituting the internal and external root 
sheaths. 

The hair protects the head from the heat of the sun and cold, retains the 
heat of the body, prevents the entrance of foreign matter into the lungs, 
nose, ears, etc. The color is due to the pigment matter, which, in old age, 
becomes more or less whitened. 

The Sebaceous Glands, imbedded in the true skin, are simple and 
compound racemose glands, opening, by a common excretory duct, upon 
the surface of the epidermis or into the hair follicle. They are found in 
all portions of the body, most abundantly in the face, and are formed by a 
delicate, structureless membrane, lined by flattened polyhedral cells. The 
sebaceous glands secrete a peculiar oily matter, the sebum , by which the 
skin is lubricated and the hairs softened ; .it is quite abundant in the region 
of the nose and forehead, which often present a greasy, glistening appear¬ 
ance ; it consists of water, mineral salts, fatty globules, and epithelial 
cells. 

The vernix caseosa which frequently covers the surface of the fetus at 
birth consists of the residue of the sebaceous matters, containing epithelial 
cells and fatty matters ; it seems to keep the skin soft and supple, and 
guards it from the effects of the long-continued action of water. 

The Sudoriparous Glands excrete the sweat; they consist of a mass 
or coil of a tubular gland duct, situated in the derma and in the subcuta¬ 
neous tissue ; average the y 1 ^ of an inch in diameter, and are surrounded by 
a rich plexus of capillary blood-vessels. From this coil the duct passes in a 
straight direction up through the skin to the epidermis, where it makes a 
few spiral turns and opens obliquely upon the surface. The sweat .glands 
consist of a delicate homogeneous membrane lined by epithelial cells, whose 
function is to extract from the blood the elements existing in the perspi¬ 
ration. 


APPENDAGES OF THE SKIN. 


129 


The glands are very abundant all over the cutaneous surface, as many as 
3528 to the square inch, according to Erasmus Wilson. 

The Perspiration is an excrementitious fluid, clear, colorless, almost 
odorless, slightly acid in reaction, with a specific gravity of 1.003 or 1.004. 

The total quantity of perspiration excreted daily has been estimated at 
about two pounds, though the amount varies with the nature of the food 
and drink, exercise, external temperature, season, etc. 

The elimination of the sweat is not intermittent, but continuous; but it 
takes place so gradually that as fast as it is formed it passes off by evapora¬ 
tion as insensible perspiration. Under exposure to great heat and exercise 
the evaporation is not sufficiently rapid, and it appears as sensible perspira¬ 
tion. 

COMPOSITION OF SWEAT. 


^ ater >. 995-573 

Urea, .. 0.043 

Fatty matters. 0.014 

Alkaline lactates,. 0.317 

Alkaline sudorates,. 1.562 

Inorganic salts,. 2.491 


1000.00 

Urea is a constant ingredient. 

Carbonic acid is also exhaled from the skin, the amount being about 
of that from the lungs. 

Perspiration regulates the temperature, and removes waste matters from 
the blood ; it is so important, that if elimination be prevented death occurs 
in a short time. 

Influence of the Nervous System.—The secretion of sweat is regu¬ 
lated by the nervous system. Here, as in the secreting glands, the fluid is 
formed from material in the lymph spaces surrounding the gland. Two 
sets of nerves are concerned, viz.: vasomotor , regulating the blood supply; 
and secretory , stimulating the activities of the gland cells. Generally the 
two conditions, increased blood flow and increased glandular action, coexist. 
At times profuse clammy perspiration occurs, with diminished blood flow. 

The dominating sweat center is located in the medulla, though subordi¬ 
nate centers are present in the cord. The secretory fibers reach the perspi¬ 
ratory glands of the head and face through the cervical sympathetic ; of the 
arms, through the thoracic sympathetic, ulnar, and radial nerves; of the 
leg, through the abdominal sympathetic and sciatic nerves. 

The sweat center is excited to action by mental emotions, increased tem¬ 
perature ’of blood circulating in the medulla and cord, increased venosity 
of blood, and many drugs, rise of external temperature, exercise, etc. 









130 


HUMAN PHYSIOLOGY. 


NERVOUS SYSTEM. 

The Nervous System codrdinates all the various organs and tissues 
of the body, and brings the individual into conscious relationship with 
external nature by means of sensation, motion, language, mental and moral 
manifestations. 

The Nervous Tissue may be divided into two systems, the Cerebro¬ 
spinal and the Sympathetic. 

(1) The Cerebro-spinal System occupies the cavities of the cranium 
and spinal canal, and consists of the brain, the spinal cord, the cranial and 
spinal nerves. It is the system of animal life, and presides over the func¬ 
tions of sensation, motion, etc. 

(2) The Sympathetic System, situated along each side of the spinal 
column, consists (1) of a double chain of ganglia, united together by nerve 
cords, and extends from the base of the cranium to the coccyx; (2) of 
various ganglia, situated in the head and face, thorax, abdomen, pelvis, etc. 
All the ganglia are united together by numerous communicating fibers, 
many of which anastomose with the fibers of the cerebro-spinal system. It 
is the nervous system of organic life, and governs the functions of nutrition, 
growth, etc. 

Nervous Tissue is composed of two kinds of matter, the gray and 
white , which differ in their color, structure, and physiological endowments; 
the former consists of vesicles or cells which receive and generate nerve 
force; the latter consists of fibers which simply conduct it, either from the 
periphery to the center or the reverse. 

Structure of Gray Matter.—The gray matter found on the surface of 
the brain in the convolutions, in the interior of the spinal cord, and in the 
various ganglia of the cerebro-spinal and sympathetic nervous systems, 
consists of a fine connective tissue stroma, the neuroglia , in the meshes of 
which are embedded the gray cells or vesicles. 

The cells are grayish in color, and consist of a delicate investing capsule 
containing a soft, granular, albuminous matter, a nucleus , and sometimes a 
nucleolus. Some of the cells are spherical or oval in shape, while others 
have an interrupted outline, on account of having one, two, or more pro¬ 
cesses issuing from them, constituting the uni-polar , bi-polar, or multi-polar 
nerve cells. Cells vary in size ; the smallest being found in the brain, the 


NERVOUS SYSTEM. 


131 


largest in the anterior horns of gray matter of the spinal cord. Some of 
the cell processes become continuous with the fibers of the white matter, 
while others anastomose with those of adjoining cells and form a plexus . 

Structure of the White Matter.—The white matter, found for the 
most part in the interior of the brain, on the surface of the spinal cord, and 
in almost all the nerves of the cerebro-spinal and sympathetic systems, 
consists of minute tubules or fibers, the ultimate nerve filaments, which in 
the perfectly fresh condition are apparently structureless and homogeneous ; 
but when carefully examined after death are seen to consist of three distinct 
portions, (i) a tubular membrane; (2) the white substance of Schwann; 
(3) the axis cylinder. 

The tubular membrane , investing the nerve filament, is thin, homoge¬ 
neous, and lined by large, oval nuclei, and presents, in its course, annular 
constrictions; it serves to keep the internal parts of the fiber in position, 
and protects them from injury. 

The white substance of Schwann, or the medullary layer , is situated 
immediately within the tubular membrane, and gives to the nerves their 
peculiar white and glistening appearance. It is composed of oleaginous 
matter in a more or less fluid condition; after death it undergoes coagula¬ 
tion, giving to the fiber a knotted or varicose appearance. It serves to 
insulate the axis cylinder, and prevents the diffusion of the nerve force. 

The axis cylbider occupies the center of the medullary substance. In 
the natural condition it is transparent and invisible, but when treated with 
proper reagents, it presents itself as a pale, granular, flattened band, albu¬ 
minous in character, more or less solid, and somewhat elastic. It is com¬ 
posed of a number of minute fibrillee united together to form a single bundle. 
(Schultze.) 

Nerve fibers in which these three structural elements coexist are known 
as the medullated nerve fibers. In the sympathetic system, and in the gray 
substance of the cerebro-spinal system, many nerves are destitute of a me¬ 
dullary layer, and are known as the non-medullated nerve fibers. 

Gray or Gelatinous nerve fibers, found principally in the sympathetic 
system, are gray in color, semi-transparent, flattened, with distinct borders, 
finely granular, and present oval nuclei. 

The diameter of the gelatinous fibers is about the jfaf of an inch; of 
the medullated fibers from to T 3otr an i nc ^* 

Ganglia are small bodies, varying considerably in size, situated on the 
posterior roots of spinal nerves, on the sensory cranial nerves, alongside of 
the vertebral column, forming a connecting chain, and in the different 


132 


HUMAN PHYSIOLOGY. 


viscera. They consist of a dense, investing, fibrous membrane, containing 
in its interior gray or vesicular cells, among which are found white and gela¬ 
tinous nerve fibers. They may be regarded as independent nerve centers. 

Structure of Nerves.—Within the cranial and spinal cavities, the nerve 
fibers are bound together by connective tissue in the form of continuous 
bundles. Through the foramina of these cavities the nerve fibers emerge 
in the form of rounded or flattened cords, which are termed nerves: Each 
nerve is surrounded by a sheath of connective tissue, the neurilemma , 
which also forms a stroma in which the blood-vessels ramify, furnishing 
nutritive material for the growth and repair of the ultimate nerve fibers. 

A nerve consists of a greater or less number of ultimate nerve filaments , 
separated into bundles by fibrous septa given off from the neurilemma. The 
nerve filaments pursue an uninterrupted course, from their origin to their 
termination; branches pass from one nerve trunk into the sheath of 
another, but there is no anastomosis or coalescence with adjoining nerve 
fibers. Nerves are channels of connection between the brain and cord, 
and the muscles, glands, skin, mucous membrane, etc., in which they ter¬ 
minate. Any excitation at either end produces in the nerve an impulse 
which travels throughout the length of the fiber. If the nerve fibers going 
to a muscle or gland are stimulated, there is increased muscular movement 
and increased secretion ; if the nerve fibers distributed to the skin or mucous 
membranes are stimulated, there is produced in the brain a sensation. This 
difference in effects produced by irritation has led to a division of fibers 
into two classes: viz., I. Efferent or motor. 2. Afferent or sensory. There 
is no anatomical or chemical difference discoverable between these two 
classes of fibers. 

A Plexus is formed by a number of branches of different nerves inter¬ 
lacing in every direction, in the most intricate manner, but from which 
fibers are again given off to pursue their independent course, e. g., brachial, 
cervical, lumbar, sacral, cardiac plexuses, etc. 

Nerve Terminations.—(1) Central. Both motor and sensory nerve 
fibers, as they enter the spinal cord and brain, lose their external invest¬ 
ments, and retaining only the axis cylinder, ultimately become connected 
with the processes of the gray cells. 

(2) Peripheral. As the nerves approach the tissues to which they are 
to be distributed, they inosculate freely, forming a plexus from which the 
ultimate fibers proceed to individual tissues. 

Motor Nerves.—In the voluntary or striped muscles the motor nerves 
are connected with the contractile substance by means of the “ motorial 


PROPERTIES AND FUNCTIONS OF NERVES. 


133 


endplates /” when the nerve enters the muscular fiber the tubular mem¬ 
brane blends with the sarcolemma, the medullary layer disappears, and the 
axis cylinder spreads out into the form of a little plate, granular in charac¬ 
ter, and containing oval nuclei. 

In the unstriped or involuntary muscles, the terminal nerve fibers form 
a plexus on the muscular fiber cells, and become connected with the granu¬ 
lar contents of the nuclei. 

In the glands nerve fibers have been traced to the glandular cells, where 
they form a branching plexus from which fibers pass into their interior and 
become connected with their substance, and thus influence secretion. 

Sensitive Nerves terminate in the skin and mucous membranes, in 
three distinct modes, e. g., as tactile corpuscles, Pacinian corpuscles, and as 
end bulbs. 

The tactile corpuscles are found in the papillae of the true skin, especially 
on the palmar surface of the hands and fingers, feet and toes; they are 
oblong bodies, measuring about 3^ of an inch in length, consisting of a 
central bulb of homogeneous connective tissue surrounded by elastic fibers 
and elongated nuclei. The nerve fiber approaches the base of the corpus¬ 
cle, makes two or three spiral turns around it, and terminates in loops. 
They are connected with the sense of touch. 

The Pacinian corpuscles are found chiefly in the subcutaneous cellular 
tissue, on the nerves of the hands and feet, the intercostal nerves, the 
cutaneous nerves, and in many other situations. They are oval in shape, 
measure about the To of an inch in length on the average, and consist of 
concentric layers of connective tissue; the nerve fiber penetrates the cor¬ 
puscle and terminates in a rounded knob in the central bulb. Their func¬ 
tion is unknown. 

The end bulbs of Krause are formed of a capsule of connective tissue in 
which the nerve fiber .terminates in a coiled mass or bulbous extremity; 
they exist in the conjunctiva, tongue, glans penis, clitoris, etc. 

Many sensitive nerves terminate in the papillae at the base of the hair 
follicle; but in the skin, mucous membranes, and organs of special sense 
their mode of termination is not well understood. 

PROPERTIES AND FUNCTIONS OF NERVES. 

Classification.—Nerves may be divided into two groups, viz.:— 

(1) Afferent or centripetal , as when they convey to the nerve centers the 
impressions which are made upon their peripheral extremities or parts of 
their course. They may be sensitive , when they transmit impressions 


134 


HUMAN PHYSIOLOGY. 


which give rise to sensations; reflective or excitant, when the impression 
carried to the nerve center is reflected outward by an efferent nerve and 
produces motion or some other effect in the part to which the nerve is dis¬ 
tributed. 

(2) Efferent or centrifugal, as when the impulses generated in the 
centers are transmitted outward to the muscles and various organs. They 
may be motor, as when they convey impulses to the voluntary and invol¬ 
untary muscles; vasomotor, when they regulate the caliber of the small 
blood-vessels, increasing or diminishing the amount of blood to a part; 
secretory, when they influence secretion; trophic, when they influence 
nutrition; inhibitory , when they conduct impulses which produce a 
restraining or inhibiting action. 

Irritability, Excitability, Neurility .—All nerves possess the property of 
being called into action by a stimulus in virtue of the possession of an 
ultimate and inherent property denominated irritability or excitability, 
which is manifested so long as the physical and chemical integrity of the 
nerve is maintained. During the period of excitement, no change in the 
nerve is appreciable except an electrical one. 

The irritability of a motor nerve is demonstrated by the contraction of 
the muscles to which it is distributed; the impulse aroused by an irritant 
travels outward to the muscles and calls forth a contraction. 

The irritability of a sensory nerve is demonstrated by the development 
of a conscious sensation. An irritation applied to a sensory nerve in any 
part of its course arouses an impulse which travels to the brain and pro¬ 
duces there a sensation. The irritability of a sensory nerve may be increased 
by congestion or inflammation and decreased by cold, compression, and 
injuries. Other tissues — e. g., muscles,.glands, etc.—possess irritability, 
and when subjected to the action of a stimulus react in their own particular 
way. The irritability of nerves is distinct and independent of the irrita¬ 
bility of muscles and glands, as can be demonstrated by the use of poisons, 
such as woorara, atropia, etc. 

The properties of sensation and motion reside in different nerve fibers. 
Motor nerves can be destroyed or paralyzed by the introduction of 
woorara under the skin, without affecting sensation; the sensibility of 
nerves can be abolished by the employment of anesthetics without destroy¬ 
ing motion. 

In the transmission of the nerve impulse the axis cylinder is the essential 
conducting agent, the white substance of Schwann and tubular membrane 
being probably accessory structures, protecting the axis from injury, and 
preventing the diffusion of nerve force to adjoining nerves. 


PROPERTIES AND FUNCTIONS OF NERVES. 


135 


Nerve Degeneration. —When nerves are separated from their trophic 
or nutritive centers, they degenerate progressively in the direction in 
which they conduct impressions. In motor nerves, from the center to the 
periphery; in sensory nerves, from the periphery to the centers. 

Stimuli of Nerves.—Nerves do not possess the power of spontaneously 
generating and propagating nerve impulses; they can only be aroused to 
activity by the action of an extra-neural stimulus. In the living condition, 
the stimuli capable of throwing the nerve into an active condition act for 
the most part on either the central or peripheral end of the nerve. In the 
case of motor nerves the stimulus to the excitation, originating in some 
molecular disturbance in the nerve cells, acts upon the nerve fibers in con¬ 
nection with them. In the case of sensory or afferent nerves the stimuli act 
upon the peculiar end organs with which the sensory nerves are in connec¬ 
tion, which in turn excite the nerve fibers. Experimentally, it can be 
demonstrated that nerves can be excited by a sufficiently powerful stimulus 
applied in any part of their extent. 

Nerves respond to stimulation according to their habitual function ; thus, 
stimulation of a sensory nerve, if sufficiently strong, results in the sensation 
of pain ; of the optic nerve, in the sensation of light; of a motor nerve, in 
contraction of the muscle to which it is distributed; of a secretory nerve, 
in the activity of the related gland, etc. It is, therefore, evident that pecu¬ 
liarity of nervous function depends neither upon any special construction or 
activity of the nerve itself, nor upon the nature of the stimulus, but entirely 
upon the peculiarities of its central and peripheral end organs. 

Nerve stimuli may be divided into: 1st, General stimuli , comprising 
those agents which are capable of exciting a nerve in any part of its course ; 
2d, Special stimuli, comprising those agents which act upon nerves only 
through the intermediation of the end organs. 

General stimuli :— 

1. Mechanical: as from a’blow, pressure, tension, puncture, etc. 

2. Thermal: heating a nerve at first increases and then decreases its 

excitability. 

3. Chemical: Sensory nerves respond somewhat less promptly than motor 

nerves to this form of irritation. 

4. Electrical: Either the constant or interrupted current. 

5. The normal physiological stimulus :— 

(1 a ) Centrifugal or afferent if proceeding from the center toward the 
periphery. 

(< 5 ) Centripetal or afferent if in the reverse direction. 


HUMAN PHYSIOLOGY. 


136 

Special Stimuli :— 

1. Light or ethereal vibrations acting upon the end organs of the optic 

nerve in the retina. 

2. Sound or atmospheric undulations acting upon the end organs of the 

auditory nerve. 

3. Heat or vibrations of the air acting upon the end organs in the skin. 

4. Chemical agencies acting upon the end organs of the olfactory and 

gustatory nerves. 

As to the nature of the nerve impulse generated by the above stimuli but 
little is known. It is supposed to be a mode of motion, molecular or 
vibratory in character, which passes through the axis cylinder with a definite 
velocity. 

Rapidity of Transmission of Nerve Force.—The passage of a ner¬ 
vous impulse, either from the brain to the periphery or in the reverse 
direction, requires an appreciable period of time. The velocity with which 
the impulse travels in human sensory nerves has been estimated at about 
190 feet per second, and for motor nerves at from 100 to 200 feet per 
second. The rate of movement is, however, somewhat modified by temper¬ 
ature, cold lessening and heat increasing the rapidity; it is also modified 
by electrical conditions, by the action of drugs, the strength of the stimulus, 
etc. The rate of transmission through the spinal cord is considerably 
slower than in nerves, the average velocity for voluntary motor impulses 
being only 33 feet per second, for sensitive impressions 40 feet, and for 
tactile impressions 140 feet per second. 

Electrical Currents in Muscles and Nerves.—If a muscle or nerve 
be divided and non-polarizable electrodes be placed upon the natural 
longitudinal surface at the equator, and upon the transverse section, elec¬ 
trical currents are observed with the aid of a delicate a galvanometer. The 
direction of the current is always from the positive equatorial surface to the 
negative transverse surface. The strength of the current increases or 
diminishes according as the positive electrode is moved toward or from 
the equator. When the electrodes are placed on the two transverse ends 
of a nerve, an axial current will be observed whose direction is opposite to 
that of the normal impulse of the nerve. 

The electromotive force of the strongest nerve current has been estimated 
to be equal to the 0.026 of a Daniell battery; the force of the current of the 
frog muscle about 0.05 to 0.08 of a Daniell. 

Negative Variation of Currents in Muscles and Nerves.—If a 
muscle or nerve be thrown into a condition of tetanus, it will be observed 


PROPERTIES AND FUNCTIONS OF NERVES. 


137 

that the currents undergo a diminution or negative variation, a change 
which passes along the nerve in the form of a wave and with a velocity 
equal to the rate of transmission of the nerve impulse. The wave length 
of a single negative variation has been estimated to be 18 millimeters; the 
period of its duration being from 0.0005 to 0.0008 of a second. 

It is asserted by Hermann that perfectly fresh, uninjured muscles and 
nerves are devoid of currents, and that the currents observed are the result 
of a molecular death at the point of section, this point becoming negative 
to the equatorial point. He applies the term “ action currents ” to the 
currents obtained when a muscle is thrown into a state of activity. 

Electrical Properties of Nerves.—When a galvanic current is made 
to flow along a motor nerve from the center to the periphery, from the 
positive to the negative poles, it is known as the direct , descending , or 
centrifugal current. When it is made to flow in the reverse direction, it 
is known as the inverse , ascending , or centripetal current. 

The passage of a direct current enfeebles the excitability of a nerve; the 
passage of the inverse current increases it. The excitability of a nerve may 
be exhausfed by the repeated applications of electricity; when thus ex¬ 
hausted it may be restored by repose, or by the passage of the inverse 
current if the nerve has been exhausted by the direct current, or vice versa. 

During the actual passage of a feeble constant current in either direction 
neither pain nor muscular contraction is ordinarily manifested ; if the current 
be very intense, the nerve maybe disorganized and its excitability destroyed. 

Electrotonus. —The passage of a direct galvanic current through a por¬ 
tion of a nerve excites in the parts beyond the electrodes a condition of 
electric tension or electrotonus , during which the excitability of the nerve 
is decreased near the anode or positive pole, and increased near the kathode 
or negative pole; the increase of excitability in the katelectrotonic area y 
that nearest the muscle, being manifested by a more marked contraction of 
the muscle than the normal, when the nerve is irritated in this region. The 
passage of an inverse galvanic current excites the same condition of elec¬ 
trotonus ; and the diminution of excitability near the anode, the anelec- 
trotonic area , that now nearest the muscle, being manifested by a less 
marked contraction than the normal when the nerve is stimulated in this 
region. Between the electrodes is a neutral point where the katelectrotonic 
area emerges into the anelectrotonic area. If the current be a strong one, 
the neutral point approaches the kathode; if w’eak, it approaches the 
anode. 

When a nervous impulse passes along a nerve, the only appreciable effect 
is a change in its electrical condition, there being no change in its tempera- 
J 


138 


HUMAN PHYSIOLOGY. 


ture, chemical composition, or physical condition. The natural nerve cur¬ 
rents, which are always present in a living nerve as a result of its nutritive 
activity, in great part disappear during the passage of an impulse, under¬ 
going a negative variation. 

Law of Contraction.—If a feeble galvanic current be applied to a 
recent and excitable nerve, contraction is produced in the muscles only upon 
the making of the circuit with both the direct and inverse currents. 

If the current be moderate in intensity, the contraction is produced in 
the muscle both upon the making and breaking of the circuit, with both 
the direct and inverse currents. 

If the current be intense , contraction is produced only when the circuit 
is made with the direct current, and only when it is broken with the inverse 
current. 

The Reaction of Degeneration.—Two different applications of elec¬ 
tricity are used in electro-physiology and electro-therapeutics—the constant 
or galvanic, and the interrupted or faradic currents. Injured and paralyzed 
muscles and nerves react differently to these two kinds of stimuli, and the 
facts are of the greatest importance in the diagnosis and therapeutics of the 
precedent lesions. The principal difference of behavior relates to the 
reaction of degeneration —a condition produced by paralysis of any kind. 
It is characterized by a diminished or abolished excitability of the muscles 
to the faradic current, while there is at the same time an increased excita¬ 
bility to the galvanic current. The synchronous diminished excitability of 
the nerves is the same for either current. The term partial reaction of 
degeneration is used when there is a normal reaction of the nerves, but the 
muscles show the degenerative reaction. This condition is a characteristic 
of progressive muscular atrophy. 


CRANIAL NERVES. 

The Cranial Nerves come off from the base of the brain, pass through 
the foramina in the walls of the cranium, and are distributed to the skin, 
muscles, and organs of sense in the face and head. 

According to the classification of Soemmering, there are 12 pairs of 
nerves, enumerating them from before backward, as follows, viz:— 

1st Pair, or Olfactory. 4 th Pair, or Patheticus, Trochlearis. 

2d Pair, or Optic. 5th Pair, or Trifacial, Trigeminus. 

3d Pair, or Motor oculi communis. 6th Pair, or Abducens. 


CRANIAL NERVES. 


139 


7th Pair, or Facial, Portio dura. loth Pair, or Pneumogastric. 

8th Pair, or Auditory, Portio mollis, nth Pair, or Spinal accessory. 

9th Pair, or Glosso-pharyngeal. 12th Pair, or Hypoglossal. 

The Cranial Nerves may also be classified physiologically, according 
to their function, into three groups : i. Nerves of special sense. 2. Nerves 
of motion. 3. Nerves of general sensibility. 

1st Pair. Olfactory. 

Apparent Origin.—From the inferior and internal portion of the ante¬ 
rior lobes of the cerebrum by three roots, viz: an external white root , which 
passes across the fissure of Sylvius to the middle lobe of the cerebrum; an 
internal white root, from the most posterior part of the anterior lobe; a 
gray root , from the gray matter in the posterior and inner portion of the 
inferior surface of the anterior lobe. 

Deep Origin.—Not satisfactorily determined. 

Distribution.—The olfactory nerve, formed by the union of the three 
roots, passes forward along the under surface of the anterior lobe to the 
ethmoid bone, where it expands into the olfactory bulb. This bulb con¬ 
tains ganglionic cells, is grayish in color and soft in consistence ; it gives off 
from its under surface from fifteen to twenty nerve filaments, the true olfac¬ 
tory nerves , which pass through the cribriform plate of the ethmoid bone, 
and are distributed to the Schneiderian mucous membrane. This membrane 
extends from the cribriform plate of the ethnoid bone downward, about one 
inch. 

Properties.—The olfactory nerves give rise to neither motor nor sensory 
phenomena when stimulated. They carry simply the special impressions 
of odorous substances. Destruction or injury of the olfactory bulbs is 
attended by a loss of. the sense of smell. 

Function.—Governs the sense of smell. Conducts the impressions 
which give rise to odorous sensations. 

2d Pair. Optic. 

Apparent Origin.—From the anterior portion of the optic commissure. 

Deep Origin.—The origins and connections of the optic tract are very 
complex. The immediate origins are bands of fibers from the thalamus 
opticus and anterior corpora quadrigemina. The corpora geniculata are 
interposed ganglia. The ultimate roots are traced— 

1. By a broad band of fibers —“ the optic radiation of Gratiolet ”—to the 
psycho-optic centers in the occipital lobes. 


140 


HUMAN PHYSIOLOGY. 


2. To the gyrus hippocampi and sphenoidal lobes. 

3. Through the corpus callosum to the motor areas of the opposite cere¬ 

bral hemispheres. 

4. To the frontal region by “ Meynert’s Commissure.” 

5. To the spinal cord. 

6. To the corpora geniculata, pulvinar, and anterior corpora geniculata 

by ganglionic roots. 

Distribution.—The two roots unite to form a flattened band, the optic 
tract, which winds around the crus cerebri to decussate with the nerve of 
the opposite side, forming the optic chiasm. The decussation of fibers is 
not complete; some of the fibers of the left optic tract going to the outer 
half of the eye of the same side, and to the inner half of the eye of the 
opposite side ; the same holds true for the right optic tract. 

The optic nerves proper arise from the commissure, pass forward through 
the optic foramina, and are finally distributed in the retince. 

Properties.—They are insensible to ordinary impressions, and convey 
only the special impressions of light. Division of one of the nerves is 
attended by complete blindness in the eye of the corresponding side. 

Hemiopia and Hemianopsia.—Owing to the decussation of the fibers 
in the optic chiasm division of the optic tract produces loss of sight in 
the outer half of the eye of the same side, and in the inner half of the 
eye of the opposite side, the blind part being separated from the normal 
part by a vertical line. The term hemiopia is applied to the loss of func¬ 
tion or paralysis of the one-half of the retina; hemianopsia is applied to the 
blindness in the field of vision. If, for example, the right optic tract be 
divided, there will be hemiopia in the outer half of the right eye and 
inner half of left eye, thus causing left lateral hemianopsia , and as the 
two halves are affected which correspond in normal vision, it is spoken of as 
homonymous hemianopsia. Lesion of the anterior part of the optic chiasm 
causes blindness in the inner half of the two eyes. 

Functions.—Governs the sense of sight. Receives and conveys to the 
brain the luminous impressions which give rise to the sensation of sight. 

The reflex movements of the iris are called forth by the optic nerve. 
When an excess of light falls upon the retina the impression is carried 
back to the tubercula quadrigemina, where it is transformed into a motor 
impulse, which then passes outward through the motor oculi nerve to the 
contractile fibers of the iris and diminishes the size of the pupil. The 
absence of light is followed by a dilatation of the pupil. 


CRANIAL NERVES. 


141 


3d Pair. Motor Oculi Communis. 

Apparent Origin.—From the inner surface of the crura cerebri. 

Deep Origin.—By three sets of filaments coming from the oculo- 
motorius nucleus, which lies under the aqueduct of Sylvius; these three 
groups of filaments are destined for the innervation of the muscles of the 
eyeball, the sphincter pupillse, and the ciliary muscle. By filaments coming 
from the lenticular nucleus, corpora quadrigemina, optic thalamus; these 
filaments converge to form a main trunk, which winds around the crus 
cerebri, in front of the pons Varolii. 

Distribution.—The nerve then passes forward, and enters the orbit 
through the sphenoidal fissure, where it divides into a superior branch dis¬ 
tributed to the superior reelus and levator palpebrce muscles; an inferior 
branch sending branches to the internal and inferior recti , and the in¬ 
ferior oblique muscles; filaments also pass into the ciliary or ophthalmic 
ganglion; from this ganglion the ciliary nerves arise which enter the eye¬ 
ball, and are distributed to the circular fibers of the iris and the ciliary 
muscle. The third nerve also receives filaments from the cavernous 
plexus of the sympathetic and from the fifth nerve. 

Properties.— Irritation of the root of the nerve produces contraction 
of the pupil, internal strabismus, muscular movements of eye, but no pain. 
Division of the nerve is followed by ptosis (falling of the upper eyelid), 
external strabismus , due to the unopposed action of the external rectus 
muscle; paralysis of the accommodation of the eye; dilatation of the 
pupil from paralysis of the circular fibers of the iris and ciliary muscle; 
and inability to rotate the eye, slight protrusion and double vision. The 
images are crossed; that of the paralyzed eye is a little above that of the 
sound, and its upper end inclined toward it. 

Function.—Governs movements of the eyeball by animating all the 
muscles except the external rectus and superior oblique, the movements of 
the iris, elevates the upper lid, influences the accommodation of the eye 
for distances. Can be called into action by (1) voluntary stimuli, (2) by 
reflex action through irritation of the optic nerve. 


4th Pair. Patheticus. 

Apparent Origin.—From the superior peduncles of the cerebellum. 
Deep Origin.—By fibers terminating in the corpora quadrigemina, 
lenticular nucleus, valve of Vieussens, and in the substance of the cerebellar 


142 


HUMAN PHYSIOLOGY. 


peduncles; some filaments pass over the median line and decussate with 
fibers of the opposite side. 

Distribution.—The nerve enters the orbital cavity through the sphe¬ 
noidal fissure, and is distributed to the superior oblique muscle; in its 
course receives filaments from the ophthalmic branch of the 5th pair and the 
sympathetic. 

Properties.—When the nerve is irritated muscular movements are pro¬ 
duced in the superior oblique muscle, and the pupil of the eye is turned 
downward and outward. Division or paralysis lessens the movements 
and rotation of the globe downward and outward. The diplopia conse¬ 
quent upon this paralysis is homonymous, one image appearing above the 
other. The image of the paralyzed eye is below, its upper end inclined 
toward that of the sound eye. 

Function.—Governs the movements of the eyeball produced by the 
action of the superior oblique muscles. 


6th Pair.* Abducens. Motor Oculi Externus. 

Apparent Origin.*—From the groove between the anterior pyramidal 
body and the pons Varolii, where it arises by two roots. 

Deep Origin.—From the gray matter of the medulla oblongata. 

Distribution.—The nerve then passes into the orbit through the sphe¬ 
noidal fissure, and is distributed to the external rectus muscle. Receives 
filaments from the cervical portion of the sympathetic, through the carotid 
plexus and spheno palatine ganglion. 

Properties.—When irritated , the external rectus muscle is thrown into 
convulsive movements, and the eyeball is turned outward. When divided 
or paralyzed , this muscle is paralyzed; motion of the eyeball outward past 
the median line is impossible, and the homonymous diplopia increases as 
the object is moved outward past this line. The images are upon the same 
plane and parallel. Internal strabismus fesults because of the unopposed 
action of the internal rectus. 

Function.—To turn the eyeball outward. 


* The 6th nerve is considered in connection with the 3d and 4th nerves, since they 
together constitute the motor apparatus by which the ocular muscles are excited to 
action. 




CRANIAL NERVES. 


143 


5th Pair. Trifacial. Trigeminal. 

Apparent Origin.—By two roots from the side of the pons Varolii. 

Deep Origin.—The deep origin of the two roots is the upper part of 
the floor and anterior wall of the 4th ventricle, by three bundles of fila¬ 
ments, one of which anastomoses with the auditory nerve; another passes 
to the lateral tract of the medulla ; while a third, grayish in color, goes to 
the restiform bodies, and may be traced to the point of the calamus scrip- 
torius. 

Filaments of origin have been traced to the “ trigeminal sensory nucleus,” 
located on a level with the point of exit of the nerve, and to the posterior 
gray horns of the cord, as low down as the middle of the neck. 

Distribution.—The large root of the nerve passes obliquely upward 
and forward to the ganglion of Gasser, which receives filaments of com¬ 
munication from the carotid plexus of the sympathetic. It then divides 
into three branches. 

1. Ophthalmic branch, which receives communicating filaments from 
the sympathetic, and sends sensitive fibers to all the motor nerves of the 
eyeball. It is distributed to the ciliary ganglion, lachrymal gland, sac and 
caruncle, conjunctiva, integument of the upper eyelid, forehead, side of 
head and nose, anterior portion of the scalp, ciliary muscle, and iris. 

2. SupeHor maxillary branch , sends branches to the spheno-palatine 
ganglion, integument of the temple and lower eyelid, side of forehead, nose, 
cheek and upper lip, teeth of the upper jaw, and alveolar processes. 

3. Inferior maxillary branch , which, after receiving in its course fila¬ 
ments from the small root and from the facial, is distributed to the sub¬ 
maxillary ganglion, the parotid and sub-lingual glands, external auditory 
meatus, mucous membrane of the mouth, anterior two-thirds of the tongue 
(lingual branch), gums, arches of the palate, teeth of the lower jaw, 
and integument- of the lower part of the face, and to the muscles of 
mastication. 

The small root passes forward beneath the ganglion of Gasser, through 
the foramen ovale, and joins the inferior maxillary division of the large 
root, which then divides into an anterior and posterior branch, the former 
of which is distributed to the muscles of mastication, viz.: temporal, mas- 
seter, internal and external pterygoid muscles. 

Properties.—It is the most acutely sensitive nerve in the body, and 
endows all the parts to which it is distributed with general sensibility. 

Irritation of the large root , or any of its branches, will give rise to 


144 


HUMAN PHYSIOLOGY. 


marked evidence of pain; the various forms of neuralgia of the head and 
face being occasioned by compression, disease, or exposure of some of its 
terminal branches. 

Division of the large root within the cranium is followed at once by a 
complete abolition of all sensibility in the head and face, but is not attended 
by any loss of motion. The integument, mucous membranes, and the eye 
may be lacerated, cut, or bruised, without the animal exhibiting any evidence 
of pain. At the same time the lachrymal secretion is diminished, the pupil 
becomes contracted, the eyeball is protruded, and the sensibility of the 
tongue is abolished. 

The reflex movements of deglutition are also somewhat impaired; the 
impression of the food being unable to reach and excite the nerve center in 
the medulla*oblongata. 

Galvanization of the small root produces movements of the muscles of 
mastication; section of the root causes paralysis of these muscles, and the 
jaw is drawn to the opposite side by the action of the opposing muscles. 

Influence of the Special Senses.—After division of the large root 
within the cranium, a disturbance in the nutrition of the special senses 
sooner or later manifests itself. 

Sight .—In the course of twenty-four hours the eye becomes very vascular 
and inflamed, the cornea becomes opaque and ulcerates, the humors are 
discharged, and the eye is totally destroyed. 

Smell .—The nasal mucous membrane swells up, becomes fungous, and 
is liable to bleed on the slightest irritation. The mucus is increased in 
amount, so as to obstruct the nasal passages ; the sense of smell is finally 
abolished. 

Hearing .—At times the hearing is impaired from disorders of nutrition 
in the middle ear and external auditory meatus. 

Alteration in the nutrition of the special senses is not marked, if the sec¬ 
tion is made posterior to the ganglion of Gasser, and to the anastomosing 
filaments of the sympathetic which join the nerve at this point; but if the 
ganglion be divided, these effects are very noticeable, due to the section of 
the sympathetic filaments. 

Function.—Gives sensibility to all parts of the head and face to which 
it is distributed; through the small root endows the masticatory muscles 
with motion; through fibers from the sympathetic governs the nutrition of 
the special senses. 


CRANIAL NERVES. 


145 


7th Pair. Portio Dura. Facial Nerve. 

Apparent Origin.—From the groove between the olivary and restiform 
bodies at the lateral portion of the medulla oblongata, and below the margin 
of the pons Varolii. 

Deep Origin.—From a nucleus of large cells in the floor of the 4th 
ventricle, below the nucleus of origin of the 6th pair, with which it is 
connected. Some filaments are traceable to the lenticular nucleus of the 
opposite side. Some of the fibers cross the median line and decussate. It 
is intimately associated with the nerve of Wrisberg at its origin. 

Distribution.—From its origin the facial nerve passes into the internal 
auditory meatus, and then, in company with the nerve of Wrisberg, enters 
the aqueduct of Fallopius. The filaments of the nerve of Wrisberg are 
supplied with a ganglion, of a reddish color, having nerve cells. These 
filaments unite with those of the root of the facial to form a common 
trunk, which emerges at the stylo-mastoid foramen. 

In the aqueduct the facial gives off the following branches, viz.:— 

1. Large petrosal nerve, which passes forward to the spheno-palatine , or 
Meckel’s ganglion, and through this to the levator palati and azygos uvulae 
muscles, which receive motor influence from this source. 

2. Small petrosal nerve, passing to the otic ganglion and thence to the 
tensor-tympani muscle, endowing it with motion. 

3. Tympanic branch, giving motion to the stapedius muscle. 

4. Chorda tympani nerve, which after entering the posterior part of the 
tympanic cavity, passes forward between the malleus and incus bones, 
through the Glaserian fissure, and joins the lingual branch of the 5th 
nerve. It is then distributed to the mucous membrane of the anterior 
two-thirds of the tongue and the submaxillary glands. 

After emerging from the stylo-mastoid foramen, the facial nerve sends 
branches to the muscles of the ear, the occipito-frontalis, the digastric, the 
palato-glossi, and palato-pharyngei; after which it passes through the parotid 
gland and divides into the temporo-facial and cervico-facial branches, which 
are distributed to the superficial muscles of^the face, viz.: occipito-frontalis, 
corrugator supercilii, orbicularis palpebrarum, levator labii superioris et 
alaeque nasi, buccinator, levator anguli oris, orbicularis oris, zygomatici, 
depressor anguli oris, platysma myoides, etc. 

Properties.—Undoubtedly a motor nerve at its origin, but in its course 
receives sensitive filaments from the 5th pair and the pneumogastric. 

Irritation of the nerve, after its emergence from the stylo-mastoid fora- 


146 


HUMAN PHYSIOLOGY. 


men, produces convulsive movements in all the superficial muscles of the 
face. Division of the nerve at this point causes paralysis of these muscles 
on the side of the section, constituting facial paralysis ; the phenomena of 
which are a relaxed and immobile condition of the same side of the face ; 
the eyelids remain open, from paralysis of the orbicularis palpebrarum; 
the act of winking is abolished; the angle of the mouth droops, and saliva 
constantly drains away; the face is drawn over to the sound side; the face 
becomes distorted upon talking or laughing; mastication is interfered with, 
the food accumulating between the gums and cheek, from paralysis of the 
buccinator muscle ; fluids escape from the mouth in drinking; articulation 
is impaired, the labial sounds being imperfectly pronounced. 

Properties of the Branches given off in the Aqueduct of Fallopius. —The 
large petrosal, when irritated, throws the levator palati and azygos uvulae 
muscles into contraction. Paralysis of this nerve, from deep-seated lesions, 
produces a deviation of the uvula to the sound side, a drooping of the palate, 
and an inability to elevate it. 

The s?nall petrosal influences hearing by animating the tensor tympani 
muscle; when paralyzed, there occurs partial deafness and an increased 
sensibility to sonorous impressions. 

The tympanitic branch animates the stapedius muscle, and influences 
audition. 

The chorda tympani influences the circulation and the secretion of 
saliva in the sub-maxillary glands, and governs the sense of taste in the 
anterior two-thirds of the tongue. Galvanization of the chorda tympani 
dilates the blood vessels, increases the quantity and rapidity of the stream 
of bihod, and increases the secretion of saliva. Division of the nerve is 
followed by contraction of the vessels, an arrestation of the secretion, and 
a diminution of the sense of taste, on .the same side. 

Function.—The facial is the nerve of expression, and coordinates the 
muscles employed to delineate the various emotions, influences the sense 
of taste, deglutition, movements of the uvula and soft palate, the tension of 
the membrana tympani, and the secretions of the sub-maxillary and parotid 
glands. Indirectly influences smell, hearing, and vision. 

8th Pair. Portio Mollis. Auditory Nerve. 

Apparent Origin.—From the upper and lateral portion of the medulla 
oblongata, just below the margin of the pons Varolii. 

Deep Origin.—By two roots from the floor of the 4th ventricle, each 
root consisting of a number of gray filaments, some of which decussate in 


CRANIAL NERVJES. 


147 


the median line ; the external root has a gangliform enlargement contain¬ 
ing fusiform nerve cells. 

Distribution.—The two roots wind around the restiform bodies and 
enter the internal auditory meatus, and divide into an anterior branch 
distributed to the cochlea, and a posterior branch distributed to the vesti¬ 
bule and semicircular canals. 

Properties.—They are soft in consistence, grayish in color, consisting 
of axis cylinders with a medullary sheath only ; they are not sensible to 
ordinary impressions, but convey the impression of sound. 

Function.—Governs the sense of hearing. Receives and conducts to 
the brain the impression of sound, which gives rise to the sensations of 
hearing. 


gth Pair. Glosso-pharyngeal. 

Apparent Origin.—Partly from the medulla oblongata and the inferior 
peduncles of the cerebellum. 

Deep Origin.—From the lower portion of the gray substance in the 
floor of the 4th ventricle. 

This nerve has two ganglia; the jugular ganglion includes only a por¬ 
tion of the root filaments; the ganglion of Andersch includes all the fibers 
of the trunk. 

Distribution.—The trunk of the nerve passes downward and forward, 
receiving near the ganglion of Andersch fibers from the facial and pneu- 
mogastric nerves. It divides into two large branches, one of which is 
distributed to the base of the tongue, the other to the pharynx. In its 
course it sends filaments to the otic ganglion; a tympanic branch which 
gives sensibility to the mucous membrane of the fenestra rotunda, fenestra 
ovalis, and Eustachian tube; lingual branches to the base of the tongue; 
palatal branches to the soft palate, uvula,and tonsils; pharyngeal branches 
to the mucous membrane of the pharynx. 

Properties .—limitation of the roots at their origin calls forth evidences 
of pain; it is, therefore, a sensory nerve, but its sensibility is not so acute 
as that of the trifacial. Irritation of the trunk after its exit from the 
cranium produces contraction of the muscles of the palate and pharynx, 
due to the presence of anastomosing motor fibers. 

Division of the nerve abolishes sensibility in the structures to which it is 
distributed, and impairs the sense of taste in the posterior third of the 
tongue (see Sense of Taste). 


148 


HUMAN PHYSIOLOGY. 


Function.—Governs sensibility of pharynx, presides partly over the 
sense of taste, and controls reflex movements of deglutition and vomiting. 

ioth Pair. Pneumogastric. Par Vagum. 

Apparent Origin.—From the lateral side of the medulla oblongata, just 
behind the olivary body. 

Deep Origin.—In the gray nuclei in the lower half of the floor of the 
4th ventricle, and in the substance of the restiform body. Some filaments 
are traced along the restiform tract, toward the cerebellum, and others to the 
median line of the floor of the 4th ventricle, where many of them decussate. 

This nerve has two ganglia; one in the jugular foramen, called the gan¬ 
glion of the root, and another outside of the cranial cavity on the trunk, 
the ganglion of the trunk. 

Distribution.—The filaments from the root unite to form a single trunk, 
which leaves the cavity of the cranium, through the jugular foramen, in 
company with the spinal accessory and glosso-pharyngeal. It soon receives 
an anastomotic branch from the spinal accessory, and afterward branches 
from the facial, the hypoglossal and the anterior branches of the two upper 
cervical nerves. 

As the nerve passes down the neck it sends off the following main 
branches:— 

1. Pharyngeal nerves , which assist in forming the pharyngeal plexus, 
which is distributed to the mucous membrane and muscles of the pharynx. 

2. Superior laryngeal nerve, which enters the larynx through the thyro¬ 
hyoid membrane, and is distributed to the mucous membrane lining the 
interior of the larynx, and to the crico-thyroid muscle and the inferior con¬ 
strictor of the pharynx. The “ depressor nerve," found in the rabbit, is 
formed by the union of two branches, one from the superior laryngeal, the 
other from the main trunk; it passes downward to be distributed to the 
heart. 

3. Inferior laryngeal, which sends its ultimate branches to all the 
intrinsic muscles of the larynx except the crico-thyroid, and to the inferior 
constrictor of the pharynx. 

4. Cardiac branches given off from the nerve throughout its course, 
which unite with the sympathetic fibers to form the cardiac plexus, to be 
distributed to the heart. 

5. Pulmonary branches, which form a plexus of nerves and are dis¬ 
tributed to the bronchi and their ultimate terminations, the lobules and air 
cells. 


CRANIAL NERVES. 


149 


From the right pneumogastric nerve branches are distributed to the 
mucous membrane and muscular coats of the stomach and intestines, to the 
liver, spleen, kidneys, and supra-renal capsules. 

Properties.—At its origin the pneumogastric nerve is sensory, as shown 
by direct irritation or galvanization, though its sensibility is not very 
marked. In its course exhibits motor properties, from anastomosis with 
motor nerves. 

The pharyngeal branches assist in giving sensibility to the mucous 
membrane of the pharynx, and influence reflex phenomena of deglutition 
through motor fibers which they contain, derived from the spinal 
accessory. 

The superior laryngeal nerve endows the upper portion of the larynx 
with sensibility; protects it from the entrance of foreign bodies; by con¬ 
ducting impressions to the medulla, excites the reflex movements of deglu¬ 
tition and respiration; through the motor filaments it contains produces 
contraction of the crico-thyroid muscle. 

Division of the “ depressor nerve” and galvanization of the central 
end, retards and even arrests the pulsations of the heart, and by depressing 
the vasomotor center diminishes the pressure of blood in the large vessels, 
by causing dilatation of the intestinal vessels through the splanchnic 
nerves. 

The infei'ior laryngeal contains, for the most part, motor fibers from 
the spinal accessory. When irritated , produces movement in the laryn¬ 
geal muscles. When divided, is followed by paralysis of these muscles, 
except the crico-thyroid, impairment of phonation, and an embarrassment 
of the respiratory movements of the larynx, and finally death, from suffo¬ 
cation. 

The cardiac branches , through filaments derived from the spinal acces¬ 
sory, exert a direct inhibitory action upon the heart. Division of the 
pneumogastrics in the neck increases the frequency of the heart’s action. 
Galvanization of the peripheral ends diminishes the heart’s pulsation, and, 
if sufficiently powerful, paralyzes it in diastole. 

The pulmonary branches give sensibility to the bronchial mucous 
membrane, and govern the movements of respiration. Division of both 
pneumogastrics in the neck diminishes the frequency of the respiratory 
movements, falling as low as four to six per minute; death usually occurs 
in from five to eight days. Feeble galvanization of the central ends of the 
divided nerves accelerates respiration; powerful galvanization retards, 
and may even arrest the respiratory movements. 

The gastric branches give sensibility to the mucous coat, and through 


150 


HUMAN PHYSIOLOGY. 


sympathetic filaments, which join the pneumogastrics high up in the neck, 
give motion .to the muscular coat of the stomach. They influence the 
secretion of gastric juice, aid the process of digestion and absorption from 
the stomach. 

The hepatic branches , probably through anastomosing sympathetic fila¬ 
ments, influence the secretion of bile, and the glycogenic function of the 
liver; division of the pneumogastrics in the neck produces congestion of 
the liver, diminishes the density of the bile, and arrests the glycogenic 
function; galvanization of the central ends exaggerates the glycogenic 
function, and makes the animal diabetic. 

The intestinal branches give sensibility and motion to the small intes¬ 
tines, and when divided, purgatives generally fail to produce purgation. 

Function.—A great sensitive nerve, which, through anastomotic fila¬ 
ments from motor sources, influences deglutition, the action of the heart, 
the circulatory and respiratory systems, voice, the secretions of the stomach, 
intestines, and various glandular organs. 

nth Pair. Spinal Accessory. 

Apparent Origin.—By two sets of filaments :— 

1. A bulbar or medullary set, four or five in number, from the lateral or 
motor tract of the lower half bf the medulla oblongata, below the origin-of 
the pneumogastric. 

2. A spinal set, from six to eight in number, from the lateral portion of 
the spinal cord, between the anterior and posterior roots of the upper four 
or five cervical nerves. 

Deep Origin.—The medullary portion arises in a nucleus in the lower 
half of the floor of the 4th ventricle, common to the pneumogastric and 
glosso-pharyngeal nerves. The spinal portion has its origin in an elongated 
nucleus lying along the external surface of the anterior cornua of the spinal 
cord, extending down to the 5th cervical vertebra. 

Distribution.—From this origin the fibers unite to form a main trunk, 
which enters the cranial cavity through the foramen magnum, where it is 
at times joined by fibers from the posterior roots of the two upper cervical 
nerves, and sends filaments to the ganglion of the root of the pneumo¬ 
gastric. After emerging from the cranial cavity through the jugular fora¬ 
men, it sends a branch to the pneumogastric, and receives others in return, 
and also from the 2d, 3d, and 4th cervical nerves. It divides into two 
branches: (1) An internal or anastomotic branch, made up of filaments 
coming principally from the medulla oblongata, and is distributed to the 


CRANIAL NERVES. 


151 


muscles of the pharynx through the pharyngeal nerves coming from the 
pneumogastric; to all the muscles of the larynx, except the crico-thyroid 
through the inferior laryngeal nerve; to the heart, by filaments which 
reach it through the pneumogastric nerve. (2) An external branch , which 
is distributed to the sterno-cleido-mastoid and trapezius muscles; these 
muscles also receiving filaments from the cervical nerves. 

Properties.—At its origin it is a purely motor nerve, but in its course 
exhibits some sensibility from anastomosing fibers. 

Destruction of the medullary root , by tearing it from its attachment by 
means of forceps, impairs the action of the muscles of deglutition, and 
destroys the power of producing vocal sounds by paralysis of the laryngeal 
muscles, without, however, interfering with the respiratory movements of 
the larynx; these being controlled by other motor nerves. The normal 
rate of movement of the heart is also impaired by destruction of the 
medullary root. 

Irritation of the external branch throws the trapezius and sterno-mastoid 
muscles into convulsive movements, though section of the nerve does not 
produce complete paralysis, as they are also supplied with motor influence 
from the cervical nerves. The sterno-mastoid and trapezius muscles per- 
orm movements antagonistic to those of respiration, fixing the head, neck, 
and upper part of the thorax, and delaying the expiratory movement during 
the acts of pushing, pulling, straining, etc., and in the production of a pro¬ 
longed vocal sound, as in singing. When the external branch alone is 
divided, in animals, they experience shortness of breath during exercise, 
from a want of coordination of the muscles of the limbs and respiration; 
and while they can make a vocal sound, it cannot be prolonged. 

Function.—Governs phonation by its influence upon the vocal move¬ 
ments of the glottis; influences the movements of deglutition, inhibits the 
action of the heart and controls certain respiratory movements associated 
with sustained or prolonged muscular efforts and phonation. 

12th Pair. Hypoglossal or Sublingual. 

Apparent Origin.—By two groups of filaments from the medulla ob¬ 
longata, in the grooves between the olivary body and the anterior pyramid. 

Deep Origin.—From the hypoglossal nucleus situated deeply in the 
substance of the medulla, on a level with the lowest portion of the floor of 
the 4th ventricle; some decussating filaments have been traced to a higher 
encephalic center. 

Distribution.—The trunk formed by a union of the root filament passes 


152 


HUMAN PHYSIOLOGY. 


out of the cranial cavity through the anterior condyloid foramen, occa¬ 
sionally receiving a filament from the lateral and posterior portion of the 
medulla oblongata. After emerging from the cranium, it sends filaments 
to the sympathetic and pneumogastric ; it anastomoses with the lingual 
branch of the 5th pair, and receives and sends filaments to the upper cer¬ 
vical nerves. The nerve is finally distributed to the sterno-hyoid, sterno¬ 
thyroid, omo-hyoid, thyro-hyoid, stylo-glossi, hyo-glossi, genio-hyoid, genio- 
hyo-glossi, and the intrinsic muscles of the tongue. 

Properties.—A purely motor nerve at its origin, but derives sensibility 
outside the cranial cavity, from anastomosis with the cervical, pneumo¬ 
gastric, and 5th nerves. 

Irritation of the nerve gives rise to convulsive movements of the tongue 
and slight evidences of sensibility. 

Division of the, nerve abolishes all movements of the tongue, and inter¬ 
feres considerably with the act of deglutition. 

When the hypoglossal nerve is involved in hemiplegia, the tip of the 
tongue is directed to the paralyzed side when the tongue is protruded; 
due to the unopposed action of the genio-hyo-glossus on the sound side. 

Articulation is considerably impaired in paralysis of this nerve; great 
difficulty being experienced in the pronunciation of the consonantal 
sounds. 

Mastication is performed with difficulty, from inability to retain the food 
between the teeth until it is completely triturated. 

Function.—Governs all the movements of the tongue and influences the 
functions of mastication, deglutition, and articulate language. 


CEREBRO-SPINAL AXIS. 

The Cerebro-spinal Axis consists of the spinal cord, medulla oblon¬ 
gata, pons Varolii, cerebellum and cerebrum, exclusive of the spinal and 
cranial nerves. It is contained within the cavities of the cranium and 
spinal column, and surrounded by three membranes, the dura mater, 
arachnoid, and pia mater, which protect it from injury and supply it with 
blood-vessels. 

The Brain and Spinal Cord are composed of both white fibers and 
collections of gray cells, and are, therefore, to be regarded as conductors of 
impressions and motor impulses, as well as generators of nerve force. 


SPINAL CORD. 


153 


MEMBRANES. 

The Dura Mater, the most external of the three, is a tough membrane, 
composed of white fibrous tissue, arranged in bundles, which interlace in 
every direction. In the cranial cavity it lines .the inner surface of the 
bones, and is attached to the edge of the foramen magnum ; sends processes 
inward, forming the falx cerebri, falx cerebelli, and tentorium cerebelli, 
supporting and protecting parts of the brain. In the spinal canal it loosely 
invests the cord, and is separated from the walls of the canal by areolar 
tissue. 

The Arachnoid, the middle membrane, is a delicate serous structure 
which envelopes the brain and cord, forming the visceral layer , and is then 
reflected to the inner surface of the dura mater, forming the parietal layer. 
Between the two layers there is a small quantity of fluid which prevents 
friction by lubricating the two surfaces. 

The Pia Mater, the most internal of the three, composed of areolar 
tissue and blood-vessels, covers the entire surface of the brain and cord, to 
which it is closely adherent, dipping down between the convolutions and 
fissures. It is exceedingly vascular, sending small blood-vessels some dis¬ 
tance into the brain and cord. 

The Cerebro-spinal Fluid occupies the sub-arachnoid space , and the 
general ventricular cavities of the brain, which communicate by an opening, 
the foramen of Magendie, in the pia mater, at the lower portion of the 
4th ventricle. This fluid is clear, transparent, alkaline, possesses a salt 
taste and a low specific gravity; it is composed largely of water, traces of 
albumin, glucose, and mineral salts. It is secreted by the pia mater; the 
quantity is estimated from two to four fluid ounces. 

The function of the cerebro-spinal fluid is to protect the brain and cord 
by preventing concussion from without; by being easily displaced into the 
spinal canal, prevents undue pressure and insufficiency of blood to the 
brain. 


SPINAL CORD. 

The Spinal Cord varies from 16 to 18 inches in length; is half an inch 
in thickness, weighs \ l / 2 oz., and extends from the atlas to the 2d lumbar 
vertebra, terminating in the filum terminate. It is cylindrical in shape, 
and presents an enlargement in the lower cervical and lower dorsal regions, 
corresponding to the origin of the nerves which are distributed to the 
upper and lower extremities. The cord is divided into two lateral halves 
K 


154 


HUMAN PHYSIOLOGY. 


by the anterior and posterior fissures. It is composed of both white or 
fibrous and gray or vesicular matter, the former occupying the exterior of 
the cord, the latter the interior, where it is arranged in the form of two 
crescents, one in each lateral half, united together by the central mass, the 
gray commissure; the white matter being united in front by the white 
commissure. 


Structure of the White Matter.—The white matter surrounding each 
lateral half of the cord is made up of nerve fibers, some of which are con¬ 
tinuations of the nerves which enter the cord, while others are derived 
from different sources. It is subdivided into: (i) An anterior column, 
comprising that portion between the anterior roots and the anterior fissure, 
which is again subdivided into two parts: (<z) an inner portion, bordering 
the anterior median fissure, the direct pyramidal tract , or column of Turck, 
containing motor fibers which do not decussate, and which extends as far 
down as the middle of the dorsal region; ( b ) an outer portion, surrounding 
the anterior cornua, known as the anterior root zone , composed of short, 
longitudinal fibers which serve to connect together different segments of 

the spinal cord. (2) A lateral 

Fig.15. 


a 


b 


column, the portion between the 
anterior and posterior roots, 
which is divisible into (a) the 
crossedpyrai 7 iidal tract , occupy¬ 
ing the posterior portion of the 
lateral column, and containing 
all those fibers of the motor tract 
which have decussated at the 
medulla oblongata; it is com¬ 
posed of longitudinally running 
fibers which are connected with 
the multipolar nerve cells of the 
anterior cornua; ( b ) the direct 
cerebellar tract , situated upon 
the surface of the lateral column, 
consisting of longitudinal fibers 
which terminate in the cere¬ 
bellum ; it first appears in the 
lumbar region, and increases as 
it passes upward ; {c) the anterior tract, lying just posterior to the anterior 
cornua. (3) A posterior column, the portion included between the posterior 
roots and the posterior fissure, also divisible into two portions, (a) an inner 



SCHEME OF THE CONDUCTING PATHS IN THE 
SPINAL CORD AT THE 3D DORSAL NERVE. 

The black part is the gray matter, v, anterior, 
hw, posterior, root; a, direct, and g, crossed, 
pyramidal tracts, b. Anterior column, 
ground bundle, c. Goll’s column d. Pos- 
tero-external column, e and f. Mixed lateral 
paths, h. Direct cerebellar tracts.— Lan- 
dois. 






SPINAL NERVES. 


155 


portion, the postero internal column , or the column of Goll, bordering the 
posterior median fissure, and [b) an external portion, the postero-external 
column, the column of Burdach, lying just behind the posterior roots. 
They are composed of long and short commissural fibers which connect 
together different segments of the spinal cord. 

Structure of the Gray Matter.—The gray matter, arranged in the 
form of two crescents, presents an anterior and. posterior horn. It is made 
up of a delicate network of fine nerve fibers (axis cylinders), supported by 
a connective tissue framework of nucleated nerve cells, which in the anterior 
horns are large and multipolar, and connected with the anterior roots of 
spinal nerves ; in the posterior horns the nerve cells are smaller, and situated 
along the inner margin, and in the caput cornu. Small cells are also found 
in the posterior vesicular columns, and in the intermediary lateral tract. 


SPINAL NERVES. 

Origin.—The spinal nerves are thirty-one in number on each side of the 
spinal cord, and arise by two roots, an anterior and posterior, from the 
anterior and posterior aspects of the cord respectively : the posterior roots 
present near their emergence from the cord a small ganglionic enlargement; 
outside of the spinal canal the two roots unite to form a main trunk, which 
is ultimately distributed to the skin, muscles, and viscera. 

The Function of the Anterior Roots is to transmit motor impulses 
from the centers outward to the periphery. Irritation of these roots, from 
whatever cause, excites convulsive movements in the muscles to which they 
are distributed; disease or division of these roots induces a condition of 
paresis or paralysis. 

The Function of the Posterior Roots is to transmit the impressions 
made upon the periphery to the centers in the spinal cord, where they 
excite motor impulses; or to the brain, in which they are translated into 
conscious sensations. Irritation of these roots gives rise to painful sensa¬ 
tions ; division of the roots abolishes all sensation in the parts to which 
they are distributed. 

The ganglion on the posterior root influences the nutrition of the sensory 
nerve; for if the nerve be separated from the ganglion, it undergoes 
degeneration in the course of a few days, in the direction in which it 
carries impressions, i. e., from the periphery to the centers; if the nerve be 
divided between the ganglion and the cord, the central end only undergoes 


156 


HUMAN PHYSIOLOGY. 


degeneration. The nutrition of the anterior root is governed by nerve cells 
in the gray matter of the cord; for if these cells undergo atrophy , or if the 
nerve be divided , it undergoes degeneration outward. 

COURSE OF THE ANTERIOR AND POSTERIOR ROOTS. 

The Anterior Roots pass through the anterior columns, horizontally, 
in straight and distinct bundles, and enter the anterior cornuse, where they 
diverge in four directions, (i) Many become connected with the prolon¬ 
gations of the multipolar nerve cells. (2) Others leave the gray matter, 
pass through the anterior white commissure, and enter the anterior columns 
of the opposite side. (3) A considerable number enter the lateral columns 
of the same side, through which they pass to the medulla oblongata, where 
they decussate and finally terminate in the corpus striatum of the opposite 
side. (4) Others traverse the gray matter horizontally, and come into 
relation with the posterior roots. 

The Posterior Roots enter the posterior horns of the gray matter (1) 
through the substantia gelatinosa, (2) through the posterior columns; of 
the fortner , some bend upward and downward, and become connected 
with the anterior cornuse; others pass through the posterior commissure to 
the opposite side; of the latter , fibers pass into the gray matter to the 
posterior vesicular columns, passing obliquely through the posterior white 
columns upward and downward for some distance, and enter the gray 
matter at different heights. 

Decussation of Motor and Sensory Fibers.—The Motor fibers, 
which conduct volitional impulses from the brain outward to the anterior 
cornuse, arise in the motor centers of the cerebrum; they then pass down¬ 
ward through the corona radiata, the internal capsule, the inferior portions 
of the crura cerebri, the pons Varolii, to the medulla oblongata, where the 
motor tract of each side divides into two portions, viz.: 1. The larger , 
containing 91 to 97 per cent, of the fibers, which decussates at the lower 
border of the medulla and passes down in the lateral colutnn of the oppo¬ 
site side, and constitutes the crossed pyramidal tract. 2. The smaller , 
containing 3 to 9 per cent, of the fibers, does not decussate, but passes down 
the anterior column of the same side, and constitutes the direct pyramidal 
tract, or the column of Tiirck. Some of the motor fibers of these two 
tracts, after entering the anterior cornuse of the gray matter, become con¬ 
nected with the large multipolar nerve cells, while others pass directly into 
the anterior roots. Through this decussation each half of the brain governs 
the muscular movements of the opposite side of the body. 


SPINAL NERVES. 


157 


Fig. i6 . 



DIAGRAM SHOWING THE COURSE, THROUGH THE SPINAL CORD, OF THE MOTOR AND 

SENSORY NERVE FIBERS. 

B and B'represent the right and left hemispheres of the brain, from which the motor 
fibers take their origin, and in which the sensory fibers terminate. The motor tract 
from the right side i passes down through the crus, through the pons to the medulla 
oblongata, where it divides into two portions : ist, the larger portion, ninety-seven 
per cent., crosses over to the opposite side of the cord and passes down through the 
lateral column. It gives off fibers at different levels, which pass into the gray matter 
and become connected with the muscles, M, through the multipolar cells ; th e smaller 
portion , three per cent., does not cross over, but descends on the same side of the 
cord in the anterior column and supplies the muscles, m. The same is true for the 
motor tract for the left hemisphere. 

The sensory fibers from the left side of the body enter the gray matter through the 
posterior roots. They then cross over at once to the opposite side of the cord and 
ascend to the hemisphere partly in the gray matter, partly in the posterior column. 
The same is true for the sensory nerves of the right side of the body. 
























































158 


HUMAN PHYSIOLOGY. 


The sensory fibers, which convey the impression made upon the peri¬ 
phery to the cord and brain, pass into the cord through the posterior roots 
of spinal nerves; they then diverge and enter the gray matter at different 
levels, and at once decussate, passing to the opposite side of the gray 
matter. The sensory tract passes upward, through the cord, the medulla, 
pons Varolii, the superior portion of the crura cerebri, the posterior third 
of the internal capsule, to the sensory perceptive center, located in the 
hippocampus major and unciate convolution (Ferrier). Through this decus¬ 
sation each half of the brain governs the sensibility of the opposite half of 
the body. 

Properties of the Spinal Cord.—Irritation applied directly to the 
antero-lateral white columns produces muscular movements but no pain; 
they are, therefore, excitable but insensible. 

The surface of the posterior columns is very sensitive to direct irritation, 
especially near the origin of the posterior roots; less so toward the posterior 
median fissure. The sensibility is due, however, not to its own proper 
fibers, but to the fibers of the posterior root which traverse it. 

Division of the antero-lateral columns abolishes all power of voluntary 
movement in the lower extremities. 

Division of th z posterior columns impairs the power of muscular coordi¬ 
nation, such as is witnessed in locomotor ataxia. 

The gray matter is probably both insensible and inexcitable under the 
influence of direct stimulation. 

A transverse section of one lateral half of the cord produces :— 

(1) On the same side, paralysis of voluntary motion and a relative or 
absolute elevation of temperature and an increased fk>w of blood in the 
paralyzed parts; hyperesthesia for the sense of contact, tickling, pain, and 
temperature. 

(2) On the opposite side, complete anesthesia as regards contact, and 
tickling and temperature, in the parts corresponding to those which are 
paralyzed in the opposite side. Complete preservation of voluntary power 
and of the muscular sense. 

A vertical section through the middle of the gray matter results in the 
loss of sensation on both sides of the body below the section, but no loss of 
voluntary power. 


FUNCTIONS OF THE SPINAL CORD. 


159 


FUNCTIONS OF THE SPINAL CORD. 

1. As a Conductor.—The lateral columns, particularly the posterior 
portions, the “ pyramidal tracts,” and the columns-of Tiirck, are the chan¬ 
nels through which pass the voluntary motor impulses from the brain to the 
large multipolar nerve cells in the anterior cornuse of gray matter, and 
through them become connected with the anterior roots which transmit the 
motor stimuli to the muscles. 

The anterior colunins, especially the portion surrounding the anterior 
cornuse, the “ anterior radicular zones,” are composed of short longitudinal 
commissural fibers, which serve to connect together different segments of 
the spinal cord, a condition required for the coordination of muscular 
movements. 

The posterior columns are composed of short and long commissural 
fibers which connect together different segments of the cord. They are 
insensible to direct irritation, but aid in the coordination of muscular move¬ 
ments in walking, standing, running, etc. Degeneration of ihe posterior 
columns gives rise to the lack of muscular coordination observed in loco¬ 
motor ataxia. 

The gray matter , and especially that portion immediately surrounding 
the central canal, transmits the sensory nerve fibers from the posterior roots 
up to the brain. Decussation of the sensory fibers takes place throughout 
the whole length of the gray matter. 

The multipolar cells of the anterior cornuce are connected with the 
generation and transmission of motor impulses outward; are centers for 
reflex movements; are the trophic centers for the motor nerves and muscu¬ 
lar fibers to which they are distributed. The anterior roots give passage 
to the vaso-constrictor and vaso-dilator fibers which exert an influence 
upon the caliber of the blood-vessels. Complete destruction of the anterior 
horns is followed by a paralysis of motion, degeneration of the anterior 
roots, atrophy of muscles and bones, and an abolition of reflex move¬ 
ments. 

2. As an Independent Nerve Center. 

The spinal cord, by virtue of its containing ganglionic nerve matter, is 
capable of transforming impressions made upon the centripetal nerves into 
motor impulses, which are reflected outward through centrifugal nerves to 
muscles, producing movements. These reflex movements taking place 
through the gray matter, are independent of sensation and volition. 

The mechanism involved in every reflex act is a sentient surface, a sen¬ 
sory nerve, a nerve center, a motor nerve, and muscle. 


160 


HUMAN PHYSIOLOGY. 


The reflex excitability of the cord may be— 

1. Increased by disease of the lateral columns, the administration of 
strychnia, and in frogs, by a separation of the cord from the brain, the latter 
apparently exerting an inhibitory influence over the former and depressing 
its reflex activity. 

2. Inhibited by destructive lesions of the cord, e.g., locomotor ataxia, 
atrophy of the anterior cornuse, the administration of various drugs, and, 
in the frog, by irritation of certain regions of the brain. When the cere¬ 
brum alone is removed and the optic lobes stimulated, the time elapsing 
between the application of an irritant to a sensory surface and the resulting 
movement will be considerably prolonged. The optic lobes (Setschenow’s 
center) apparently generating impulses which, descending the cord, retard 
its reflex movement. 

All movements taking place through the nervous system, are of this reflex 
character, and may be divided into excito viotor , sensori-motor, and ideo- 
?notor. 

Classification of Reflex Movements. (Kiiss.) They may be divided 
into four groups, according to the route through which the centripetal and 
centrifugal impulses pass. 

1. Those normal reflex acts, e.g., deglutition, coughing, sneezing, walk¬ 
ing, etc., pathological reflex acts, e. g., tetanus, vomiting, epilepsy, which 
take place both centripetally and centrifugally, through spinal nerves. 

2. Reflex acts which take place in a centripetal direction through a 
cerebro spinal sensory nerve, and in a centrifugal direction through a sym¬ 
pathetic motor nerve, usually a vasomotor nerve, e.g., the normal reflex 
acts, which give rise to most of the secretions, pallor, and blushing of the 
skin, certain movements of the iris, certain modifications in the beat of the 
heart; the pathological, which, on account of the difficulty in explaining 
their production, are termed metastatic, eg ., ophthalmia, coryza, orchitis, 
which depend on a reflex hyperemia; amaurosis, paralysis, paraplegia, etc., 
due to a reflex anemia. 

3. Reflex movements, in which the centripetal impulse passes through a 
sympathetic nerve, and the centrifugal through a cerebro-spinal nerve; 
most of these phenomena are pathological, e.g., convulsions from 
intestinal irritation produced by the presence of worms, eclampsia, hysteria, 
etc. 

4. Reflex actions, in which both the centripetal and centrifugal impulses 
pass through filaments of the sympathetic nervous system, e.g., those 
obscure reflex actions which preside over the secretions of the intestinal 
fluids, which unite the phenomena of the generative organs, the dilatation 


FUNCTIONS OF THE SPINAL CORD. 


161 


of the pupils from intestinal irritation (worms), and many pathological 
phenomena. 

Laws of Reflex Action. (Pfliiger.) 

1. Law of Unilaterality. —If a feeble irritation be applied to one or 
more sensory nerves, movement takes place usually on one side only, and 
that upon the same side as the irritation. 

2. Law of Symmetry. —If the irritation becomes sufficiently intense, 
motor reaction is manifested, in addition, in corresponding muscles of the 
opposite side of the body. 

3. Law of Intensity. —Reflex movements are usually more intense on the 
side of the irritation; at times the movements of the opposite side equal 
them in intensity, but they are usually less pronounced. 

4. Law of Radiation. —If the excitation still continues to increase, it 
is propagated upward, and motor reaction takes place through cenirifugal 
nerves coming from segments of the cord higher up. 

5. Imw of Generalization. —When the irritation becomes very intense, it 
is propagated to the medulla oblongata; motor reaction then becomes gen¬ 
eral, and it is propagated up and down the cord, so that all the muscles of 
the body are thrown into action, the medulla oblongata acting as a focus 
whence radiate all reflex movements. 

Special Reflex Movements. 

There are a number of reflex movements taking place through, the spinal 
cord, a study of which enables the physician to determine the condition of 
its different segments. They may be divided into, 1. Skin or superficial, 
and 2. Tendon or deep reflexes. The skin reflexes are induced by irritation 
of the skin and mucous membranes, e.g ., pricking, pinching, scratching, 
etc. The following are the principal skin reflexes:— 

1. Plantar reflex , consisting of contraction of the muscles of the foot, 
induced by stimulation of the sole of the foot; it involves the integrity of 
the reflex arc through the lower end of the cord. 

2. Gluteal reflex, consisting of contraction of the glutei muscles when 
the skin over the buttock is stimulated; it takes place through the segments 
giving origin to the fourth and fifth lumbar nerves. 

3. Cremasteric reflex, consisting of a contraction of the cremaster muscle, 
and a retraction of the testicle toward the abdominal ring, when the skin 
on the inner side of the thigh is stimulated; it depends upon the integrity 
of the segments giving origin to the first and second lumbar nerves. 

4. Abdo 7 ninal reflex, consisting of a contraction of the abdominal mus¬ 
cles when the skin upon the side of the abdomen is gently scratched; its 


102 


HUMAN PHYSIOLOGY. 


production requires the integrity of the spinal segments from the eighth to 
the twelfth. 

5. Epigastric reflex , consisting of a slight muscular contraction in the 
neighborhood of the epigastrium when the skin between the fourth and 
sixth ribs is stimulated; it requires the integrity of the cord between the 
fourth and seventh dorsal nerves. 

6. Scapular reflex consists of a contraction of the scapular muscles 
when the skin between the scapula is stimulated; it depends upon the 
integrity of the cord between the fifth cervical and third dorsal nerves. 

The superficial reflexes, though variable, are generally present in health. 
They are increased or exaggerated when the gray matter of the cord is 
abnormally excited, as in tetanus, strychnia poisoning, and in disease of the 
lateral columns, leading to arrest of their normal functions. The tendon 
or deep reflexes are also of great value in diagnosing the condition of the 
spinal segments. They are induced by a sharp blow upon a tendon. The 
following are the principal forms :— 

1. Patella reflex or knee jerk , consisting of a contraction of the extensor 
muscles of the thigh when the ligamentum patella is struck between the 
patella and tibia. This reflex is best observed when the legs are freely 
hanging over the edge of a table. The patella reflex is generally present 
in health, being absent in only 2 per cent.; it is greatly exaggerated in 
lateral sclerosis, in descending degeneration of the cord; it is absent in 
locomotor ataxia and in atrophic lesions of the anterior gray corn use. 

2. Ankle Jerk or Reflex. —If the extensor muscles of the leg be placed 
upon the stretch and the tendo-achillis be sharply struck, a quick extension 
of the foot will take place. 

3. Ankle - Clonus. —This consists of a series of rhythmical reflex con¬ 
tractions of the gastrocnemius muscle, varying in frequency from 6 to 10 
per second. To elicit this reflex, pressure is made upon the sole so as to 
suddenly and energetically flex the foot at the ankle, thus putting the 
tendo achillis upon the stretch. The rhythmical movements thus pro¬ 
duced continue so long as the tension is maintained. Ankle clonus is 
never present in health, but is very marked in lateral sclerosis of the cord. 

The toe reflex , peroneal reflex, wrist reflex , are also present in sclerosis 
of the lateral columns and in the late rigidity of hemiplegia. 

Special Nerve Centers in Spinal Cord.—Throughout the spinal cord 
there are a number of special nerve centers, capable of being excited 
reflexly and producing complex coordinated movements. Though for the 
most part independent in action they are subject to the controlling influences 
of the medulla and brain. 


FUNCTIONS OF THE SPINAL CORD. 


163 


1. Cilio-spinal center, situated in the cord between the lower cervical 
and third dorsal vertebra. It is connected with the dilatation of the pupil 
through fibers which emerge in this region and enter the cervical sympa¬ 
thetic. Stimulation of the cord in this locality causes dilatation of the 
pupil on the same side; destruction of the cord is followed by contraction 
of the pupil. 

2. Genito-spinal center, situated in the lower part of the cord. This is 
a complex center and comprises a series of subordinate centers for the con¬ 
trol of the muscular movements involved in the acts of defecation, micturi¬ 
tion, ejaculation of semen, the movements of the uterus during parturition, 
etc. 

3. Vasomotor centers, giving origin to both vaso-constrictor and vaso¬ 
dilator fibers, which are distributed throughout the cord. Though acting 
reflexly they are under the dominating influence of the center in the me¬ 
dulla. 

4. Sweat centers are also present in various parts of the cord. 

Paralysis from Injuries of the Spinal Cord. 

Seat of Lesion. —If it be in the lower part of the sacral canal, there is 
paralysis of the compressor urethrae, accelerator urinae, and sphincter ani 
muscles; no paralysis of the muscles of the leg. 

At the Upper Limit of the Sacral Region. —Paralysis of the muscles of 
the bladder, rectum, and anus; loss of sensation and motion in the muscles 
of the legs, except those supplied by the anterior crural and obturator, viz.: 
psoas iliacus, Sartorius, pectineus, adductor longus, magnus and brevis, 
obturator, vastus externus and internus, etc. 

At the Upper Limit of the Lumbar Region. —Sensation and motion para¬ 
lyzed. in both legs; loss of power over the rectum and bladder; paralysis 
of the muscular walls of the abdomen interfering with expiratory move¬ 
ments. 

At the Lower Portion of the Cervical Region. —Paralysis of the legs, 
etc., as above ; in addition, paralysis of all the intercostal muscles and con¬ 
sequent interference with respiratory movements; paralysis of muscles of 
the upper extremities, except those of the shoulders. 

Above the Middle of the Cervical Region. —In addition to the preceding, 
difficulty of deglutition and vocalisation, contraction of the pupils, paralysis 
of the diaphragm, scalene muscles, intercostals, and many of the accessory 
respiratory muscles; death resulting immediately from arrest of respiratory 
movements. 


164 


HUMAN PHYSIOLOGY. 


MEDULLA OBLONGATA. 

The Medulla Oblongata is the expanded portion of the upper part of 
the spinal cord. It is pyramidal in form and measures one and a half 
inches in length, three-quarters of an inch in breadth, half an inch in 
thickness, and is divided into two lateral halves by the anterior and pos¬ 
terior median fissures, which are continuous with those of the cord. Each 


Fig. 17. 



VIEW OF CEREBELLUM IN SECTION, AND OF FOURTH VENTRICLE, WITH THE 

neighboring parts. (From Sappey.) 

i. Median groove fourth ventricle, ending below in the calamus scriptorius , with the 
longitudinal eminences formed by the fasciculi teretes, one on each side. 2. The 
same groove, at the place where the white streaks of the auditory nerve emerge from 
it to cross the floor of the ventricle. 3. Inferior peduncle of the cerebellum, formed 
by the restiform body. 4. Posterior pyramid : above this is the calamus scriptorius. 
5. Superior peduncle of cerebellum, or processus e cerebello ad testes. 6, 6. Fillet to 
the side of the crura cerebri. 7, 7. Lateral grooves of the crura cerebri. 8. Corpora 
quadrigemina .—After Hirschfeld and Leveille. 


half is again subdivided by minor grooves, into four columns, viz.: anterior 
pyramid , lateral tract and olivary body , restiform body and posterior 
pyramid. k 

1. The anterior pyramid is composed partly of fibers continuous with 
those of the anterior column of the spinal cord; but mainly of fibers de¬ 
rived from the lateral tract of the opposite side, by decussation. The 













MEDULLA OBLONGATA. 165 

united fibers then pass upward through the pons Varolii and crura cerebri, 
and for the most part terminate in the corpus striatum and cerebrum. 

2. The lateral tract is continuous with the lateral columns of the cord ; 
its fibers in passing upward take three directions, viz.: an external bundle 
joins the restiform body, and passes into the cerebellum; an internal bundle 
decussates at the median line and joins the opposite anterior pyramid ; a 
middle bundle ascends beneath the olivary body, behind the pons, to the 
cerebrum, as the fasciculus teres. 

The olivary body of each side is an oval mass, situated between the 
anterior pyramid and restiform body; it is composed of white matter exter¬ 
nally and gray matter internally, forming the corpus dentatum. 

3. The restiform body, continuous with the posterior column of the cord, 
also receives fibers from the lateral column. As the restiform bodies pass 
upward they diverge and form a space, the 4th ventricle, the floor of 
which is formed by gray matter, and then turn backward and enter the 
cerebellum. 

4. The posterior pyramid is a narrow, white cord bordering the posterior 
median fissure ; it is continued upward, in connection with the fasciculus 
teres , to the cerebrum. 

The Gray Matter of the medulla is continuous with that of the cord. 
It is arranged with much less regularity, becoming blended with the white 
matter of the different columns, with the exception of the anterior. By the 
separation of the posterior columns, the transverse commissure is exposed, 
forming part of the floor of the 4th ventricle; special collections of gray 
matter are found in the posterior portions of the medulla, connected with 
the roots of origin of different cranial nerves. 

Properties and Functions.—The medulla is excitable anteriorly, and 
sensitive posteriorly to direct irritation. It serves (1) as a conductor of sen¬ 
sitive impressions upward from the cord, through the gray matter to the 
cerebrum; (2) as a conductor of voluntary impulses from the brain to the 
spinal cord and nerves, through its anterior pyramids ; (3) as a conductor 
of coordinating impulses from the cerebellum, through the restiform bodies 
to the spinal cord. 

As an Independent Reflex Center.—The medulla oblongata con¬ 
tains special collections of gray matter, which constitute independent 
nerve centers which preside over different.functions, some of which are as 
follows, viz.:— 

I. A center which controls the movements of mastication , through 
afferent and efferent nerves. (See page 63.) 


V 


166 


HUMAN PHYSIOLOGY. 


2. A center reflecting impressions which influence the secretion of saliva. 
(See page 66.) 

3. A center for sucking , mastication , and deglutition , whence are derived 
motor stimuli exciting to action and coordinating the muscles of the palate, 
pharynx, and esophagus, necessary for the swallowing of the food. The 
secretion of saliva is also controlled by a center in the medulla. 

NERVOUS CIRCLE OF DEGLUTITION. (2d and 3d Stages.) 

Excitor 
or 

Centripetal 
Nerves. 

Motor 
or 

Centrifugal 
Nerves. 

4. A center 
vomiting. 

5. A speech center , coordinating the various muscles necessary for the 
accomplishment of articulation through the hypoglossal, facial nerves, and 
the 2d division of the 5th pair. 

6. A center for the harmonization of muscles concerned in expi'ession , 
reflecting its impulses through the facial nerve. 

7. A cardiac center , which exerts (1) an accelerating influence over the 
heart’s pulsations through accelerating nerve fibers emerging from the cer¬ 
vical portion of the cord, entering the inferior cervical ganglion, and thence 
passing to the heart; (2) an inhibitory or retarding influence upon the action 
of the heart, through fibers of the spinal accessory nerve running in the 
trunk of the pneumogastric. The cardio-inhibitory center is in a state of 
tonic excitement and continuously sending impulses to the heart which 
exert an inhibitory influence upon its action. It may be stimulated directly 
by anemia as well as venous hyperemia of the blood-vessels of the medulla 
and increased venosity of the blood. It is excited reflexly by the stimula¬ 
tion of the central end of the vagus, sciatic, and splanchnic nerves. 

8. A vasomotor center , which by alternately contracting and dilating 
the blood-vessels through nerves distributed in their walls, regulates the 
quantity of blood distributed to an organ or tissue, and thus influences 
nutrition, secretion, and calorification. The vasomotor center is situated in 
the medulla oblongata and pons Varolii, between the corpora quadrigemina 

J 


f Palatal branch of 5th pair. 

Pharyngeal branches of the glosso-pharyngeal. 

Superior laryngeal branches of the pneumogastric. 
Esophageal branches of the pneumogastric. 

f Pharyngeal branches of the pneumogastric, derived 
from the spinal accessory, 
j Hypoglossal and branches of the cervical plexus, 
j Inferior or recurrent laryngeal. 

Motor filaments of the 3d division of the 5th pair. 

[ Portio dura. 

which coordinates the muscles concerned in the act of 


MEDULLA OBLONGATA. 


167 


and the calamus scriptorius. The vasomotor fibers having their origin in 
this center descend through the interior of the cord, emerge through the 
anterior roots of spinal nerves, enter the ganglia of the sympathetic, and 
thence pass to the walls of the blood-vessels, and maintain the arterial 
tonus; they may be divided into two classes, viz.: vasodilators, e.g ., 
chorda tympani, and vaso-constriciors , e.g., sympathetic fibers. 

Division of the cord at the lower border of the medulla is followed by a 
dilatation of the entire vascular system and a marked fall of the blood pres¬ 
sure. Galvanic stimulation of the divided surface of the cord is followed 
by a contraction of the blood-vessels and a rise in the blood pressure. 

The vasomotor center is stimulated directly by the condition of the 
blood in the medulla oblongata. When it is highly venous it becomes very 
active and the blood-vessels throughout the body are contracted and the 
blood current becomes swifter; sudden anemia of the medulla has a similar 
effect. This center may be increased in action with attendant rise of 
blood pressure, by irritation of certain afferent nerve fibers. These are 
known as pressor fibers. On the other hand, its action may be depressed 
by other afferent fibers with attendant fall of blood pressure. These are 
known as depressor fibers. 

9. A diabetic center, irritation of which causes an increase in the amount 
of urine secreted, and the appearance of a considerable quantity of sugar. 

10. Respiratory center, situated near the origin of the pneumogastric 
nerves, presides over the movements of respiration and its modifications, 
laughing, singing, sobbing, sneezing, etc. It may be excited rejlexly by 
the presence of carbonic acid in the lungs irritating the terminal pneumo¬ 
gastric filaments; or automatically, according to the character of the blood 
circulating through it; an excess of carbonic acid or a diminution of oxygen 
increasing the number of respiratory movements; a reverse condition dimin¬ 
ishing the respiratory movements. 

11. A spasm center, stimulation of which gives rise to convulsive phe¬ 
nomena, such as coughing, sneezing, etc. 

12. A center for certain ocular functions, governing the closure of the 
eyelids and dilatation of the pupil. 

13. A sweat center is also localized in the medulla. 


NERVOUS CIRCLE OF RESPIRATION (ENTIRELY REFLEX). 


Excitor 

or 

Centripetal 

Nerves. 


Pulmonary branches of the pneumogastric. 
Superior laryngeal. 

Trifacial, or 5th pair. 

Nerves of general sensibilty. 

Sympathetic nerve. 



168 


HUMAN PHYSIOLOGY. 


Motor 

or 

Centrifugal 

Nerves. 


Phrenic, distributed to the diaphragm. 

Intercostals, distributed to the intercostal muscles. 

Facial nerve, or portio dura, to the facial muscles, 
j External branch of spinal accessory, to the trapezius and 
sterno-cleido-mastoid muscles. 


PONS VAROLII. 

The Pons Varolii unites together the cerebrum above, the cerebellum 
behind, and the medulla oblongata below. It consists of transverse and 
longitudinal fibers, amidst which are irregularly scattered collections of gray 
or vesicular nervous matter. * 

The transverse fibers unite the two lateral halves of the cerebellum. 

The longitudinal fibers are continuous (i) with the anterior pyramids 
of the medulla oblongata, which interlacing with the deep layers of the 
transverse fibers, ascend to the crura cerebri, forming their superficial or 
fasciculated portions; (2) with fibers derived from the olivary fasciculus, 
some of which pass to the tubercula iquadrigemina, while others, uniting 
with fibers from the lateral and posterior columns of the medulla, ascend 
in the deep or posterior portions of the crura cerebri. 

Properties and Functions.—The superficial portion is insensible and 
inexcitable to direct irritation; the deeper portion appear to be excitable , 
consisting of descending motor fibers; the posterior portions are sensible 
but inexcitable to irritation. 

Transmits motor impulses and sensory impressions from and to the 
cerebrum. 

The gray ganglionic matter consists of centers which convert impressions 
into conscious sensations, and originate motor impulses, these taking place 
independent of any intellectual process; they are the seat of instinctive 
reflex acts; the centers which assist in the coordination of the automatic 
movements of station and progression. 


CRURA CEREBRI. 

The Crura Cerebri are largely composed of the longitudinal fibers ol 
the pons (anterior pyramids, fasciculi teretes); after emerging from the pons 
they increase in size, and become separated into two portions by a layer of 
dark gray matter, the locus niger. 

The superficial portion, the crusta, composed of the anterior pyramids, 
constitute the motor tract, which terminates, for the most part, in the cor- 



CORPORA QUADRIGEMINA. 


169 


pus striatum , but to some extent, also, in the cerebrum; the deep portion , 
made up of the fasciculi teretes and posterior pyramids and accessory fibers 
from the cerebellum, constitute the sensory tract (the tegmentum)., which 
terminates in the optic thala?nus and cerebrum. 

Function.—The crura are conductors of motor impulses and sensory 
impressions; the gray matter, the locus niger, assists in the coordination of 
the complicated movements of the eyeball and iris, through the motor oculi 
communis nerve. They also assist in the harmonization of general muscular 
movements, section of one crus giving rise to peculiar movements of rota¬ 
tion and somersaults forward and backward. 


CORPORA QUADRIGEMINA. 

The Corpora Quadrigemina are four small, rounded eminences, two 
on each side of the median line, situated immediately behind the third 
ventricle, and beneath the posterior border of the corpus callosum. 

The anterior tubercles are oblong from before backward, and larger than 
the posterior , which are hemispherical in shape ; they are grayish in color, 
but consist of white matter externally and gray matter internally. 

Both the anterior and posterior tubercles are connected with the optic 
thalami by commissural bands named the anterior and posterior brachia, 
respectively. They receive fibers from the olivary fasciculus and fibers 
from the cerebellum, which pass upward to enter the optic thalami. 

The corpora geniculata are situated, one on the inner side and one on 
the outer side of each optic tract, behind and beneath the optic thalamus, 
and from their position are named the corpora geniculata interna and 
externa ; they give origin to fibers of the optic nerve. 

Functions.—The Tubercula quadrigemina are the physical centers of 
sight, translating the luminous impressions into visual sensations. Destruc¬ 
tion of these tubercles is immediately followed by a loss of the sense of 
sight; moreover, their action in vision is crossed, owing to the decussation 
of the optic tracts, so that if the tubercle of the right side be destroyed by 
disease or extirpated, in a pigeon, the sight is lost in the eye of the oppo¬ 
site side, and the iris loses its mobility. 

The tubercula quadrigemina as nerve centers preside over the reflex 
movements which cause a dilatation or contraction of the iris, irritation of 
the tubercles Causing contraction, destruction causing dilatation. Removal 
of the tubercles on one side produces a temporary loss of power of the 
opposite side of the body, and a tendency to move around an axis is mani- 
L 


170 


HUMAN PHYSIOLOGY. 


fested, as after a section of one crus cerebri, which, however, may be due 
to giddiness and loss of sight. 

They also assist in the coordination of the complex movements of the 
eye, and regulate the movements of the iris during the movements of 
accommodation for distance. 


CORPORA STRIATA AND OPTIC THALAMI. 

The Corpora Striata are two large ovoid collections of gray matter, 
situated at the base of the cerebrum, the larger portions of which are 
imbedded in the white matter, the smaller portions projecting into the 
anterior part of the lateral ventricle. Each striated body is divided, by a 
narrow band of white matter, into two portions, viz.:— 

1. The caudate nucleus , the intraventricular portion, which is conical 
in shape, having its apex directed backward, as a narrow, tail-like process. 

2. The lenticular nucleus , imbedded in the white matter, and for the 
most part external to the ventricle; on the outer side of the lenticular 
nucleus is found a narrow band of white matter, the external capsule; and 
between it and the convolutions of the island of Reil, a thin band of gray 
matter, the claustrum ; the corpora striata are grayish in color, and when 
divided present transverse striations, from the intermingling of white fibers 
and gray cells. 

The Optic Thalami are two oblong masses situated in the ventricles 
posterior to the corpora striata, and resting upon the posterior portion of the 
crura cerebri. The internal surface projecting into the lateral ventricles is 
white, but the interior is grayish, from a commingling of both white fibers 
and gray cells. Separating the lenticular nucleus from the caudate nucleus 
and the optic thalamus is a band of white tissue, the internal capsule. 

The internal capsule is a narrow, bent tract of white matter, and is, for 
the most part, an expansion of the motor tract of the crura cerebri. It 
consists of two segments, an anterior , situated between the caudate nucleus 
and the anterior surface of the lenticular nucleus, and a posterior , situated 
between the optic thalamus and the posterior surface of the lenticular 
nucleus. These two segments unite at an obtuse angle, which is directed 
toward the median line. Pathological observation has shown that the 
nerve fibers of the direct and crossed pyramidal tracts can be traced upward 
through the anterior two-thirds of the posterior segment, into the centrum 
ovale, where, for the most part, they are lost; a portion, however, remain- 


CEREBELLUM. 


171 


ing united, ascend higher and terminate in the paracentral lobule, the 
superior extremity of the ascending frontal and parietal convolutions. 
The sensory tract can be traced upward, through the posterior third, into 
the cerebrum, where they probably terminate in the hippocampus major and 
unciate convolution. 

Functions.—The corpora striata are the centers in which terminate 
some of the fibers of the superficial or motor tract of the crura cerebri; 
others pass upward through the internal capsule, to be distributed to the 
cerebrum. It might be inferred, from their anatomical relations, that they 
are motor centers. Irritation by a weak galvanic current produces mus¬ 
cular movements of the opposite side of the body; destruction of their 
substance by a hemorrhage, as in apoplexy, is followed by a paralysis of 
motion of the opposite side of the body, but there is no loss of sensation. 
When the hemorrhagic destruction involves the fibers of the anterior two- 
thirds of the posterior segment of the internal capsule, and thus separates 
them from their trophic centers in the cortical motor region, a descending 
degeneration is established, which involves the direct pyramidal tract of the 
same side and the crossed pyramidal tract of the opposite side. 

Destruction of the posterior one-third of the posterior segment of the 
internal capsule is followed by a loss of sensation on the opposite side of 
the body, and a loss of the senses of smell and vision on the same side 
(Charcot). The precise function of the corpora striata is unknown, but 
they are in some way connected with motion. 

The optic thalami receives the fibers of the tegmentum, the posterior por¬ 
tion of the crura cerebri. They are insensible and inexcitable to direct 
irritation. Removal of one optic thalamus, or destruction of its substance by 
disease or hemorrhage, is followed by a loss of sensibility of the opposite 
side of the body, but there is no loss of motion ; their precise function is 
also unknown, but in some way connected with sensation. In both cases 
their action is crossed. 


CEREBELLUM. 

The Cerebellum is situated in the inferior fossae of the occipital bone, 
beneath the posterior lobes of the cerebrum. It attains its maximum 
weight, which is about 5 ozs., between the twenty-fifth and fortieth years, 
the proportion between the cerebellum and cerebrum being 1 to 8f. 

It is composed of two lateral hemispheres and a central elongated lobe, 
the vermiform process; the two hemispheres are connected with each other 
by the fibers of the middle peduncle forming the superficial portion of the 


172 


HUMAN PHYSIOLOGY. 


pons Varolii. It is brought into connection with the medulla oblongata 
and spinal cord through the prolongation of the restiform bodies; with 
the cerebrum, by fibers passing upward beneath the corpora quadrigemina 
and the optic thalami, and then forming part of the diverging cerebral 
fibers. 

Structure.—It is composed of both white and gray matter, the former 
being internal, the latter external, and convoluted, for economy of space. 

The White matter consists of a central stem, the interior of which is a 
dentated capsule of gray matter, the corpus dentatum. From the external 
surface of the stem of white matter processes are given off, forming the 
lamince , which are covered with gray matter. 

The Gray matter is convoluted and covers externally the laminated pro¬ 
cesses; a vertical section through the gray matter reveals the following 
structures:— 

1. A delicate connective tissue layer, just beneath the pia mater, contain¬ 
ing rounded corpuscles, and branching fibers passing toward the external 
surface. 

2. The cells of Purkinje , forming a layer of large, nucleated, branched 
nerve cells sending off processes to the external layer. 

3. A granular layer of small, but numerous corpuscles. 

4. Nerve fiber layer , formed by a portion of the white matter. 

Properties and Functions.—Irritation of the cerebellum is not fol¬ 
lowed by any evidences either of pain or convulsive movements; it is, 
therefore, insensible and inexcitable. 

Co-ordination of Movements.—Removal of the superficial portions 
of the cerebellum in pigeons produces feebleness and want of harmony in 
the muscular movements; as successive slices are removed, the movements 
become more irregular, and the pigeon becomes restless; when the last 
portions are removed, all power of flying , walking, standing, etc., is en¬ 
tirely gone, and the equilibrium cannot be maintained, the power of coor¬ 
dinating muscular movements being entirely gone. The same results have 
been obtained by operating on all classes of animals. 

The following symptoms were noticed by Wagner, after removing the 
whole or a large part of the cerebellum. 1. A tendency on the part of the 
animal to throw itself on one side, and to extend the legs as far as possible. 
2. Torsion of the head on the neck. 3. Trembling of the muscles of the 
body, which was general. 4. Vomiting and occasionally liquid evacua¬ 
tions. 

Forced Movements.—Division of one crus cerebelli causes the animal 


CEREBRUM. 


173 


to fall on one side and roll rapidly on its longitudinal axis. According to 
Schiff, if the peduncle be divided from behind , the animal falls on the same 
side as the injury; if the section be made in front , the animal turns to the 
opposite side. 

Disease of the cerebellum partially corroborates the result of experi- 
ments; in many cases symptoms of unsteadiness of gait, from a want of 
coordination , have been noticed. 

Comparative anatomy reveals a remarkable correspondence between the 
development of the cerebellum and the complexity of muscular actions. 
It attains a much greater development, relatively to the rest of the brain, in 
those animals whose movements are very complex and varied in character, 
such as the kangaroo, shark, and swallow. 

The cerebellum may possibly exert some influence over the sexual func¬ 
tion, but physiological and pathological facts are opposed to the idea of its 
being the seat of the sexual instinct. It appears to be simply a center for 
the coordination and equilibration of muscular movements. 


CEREBRUM. 

The Cerebrum is the largest portion of the encephalic mass, constitut¬ 
ing about four-fifths of its weight; the average weight in the adult male is 
from 48 to 50 ozs., or about three pounds, while in the adult female it is 
about five ozs. less. After the age of forty the weight of the cerebrum 
gradually diminishes at the rate of one ounce every ten years. In idiots 
the brain weight is often below the normal, at times not amounting to more 
than twenty ounces. 

The Blood Supply to the cerebrum is unusually large, considering its 
comparative bulk, nearly one-fifth of the entire volume of blood being dis¬ 
tributed to it by the carotid and vertebral arteries. These vessels anasto¬ 
mose so freely, and are so arranged within the cavity of the cranium, that 
an obstruction in one vessel will not interfere with the regular supply of 
blood to the parts to which its branches are distributed. A diminished 
amount, or complete cessation, of the supply of blood is at once followed 
by a suspension of its functional activity. 

The cerebrum is connected with the pons Varolii and medulla oblongata 
through the crura cerebri, and with the cerebellum through the superior 
peduncles. It is divided into two lateral halves, or hemispheres, by the 
longitudinal fissure running from before backward in the median line ; each 
hemisphere is composed of both white and gray matter, the former being 


174 


HUMAN PHYSIOLOGY. 


internal, the latter external; it covers the surfaces of the hemisphere which 
are infolded, forming convolutions, for economy of space. 

Fissures. 

1. The fissure of Sylvius is one of the most important; it is the first to 
appear in the development of the fetal brain, being visible at about the 
third month; in the adult it is quite deep and well marked, running from 
the under surface of the brain upward, outward, and backward, and forms 
a boundary between the frontal and temporo-sphenoidal lobes. 

2. The fissure of Rolando is second in importance, and runs from a point 
on the convexity near the median line transversely outward and downward 
toward the fissure of Sylvius, but does not enter it. It separates the frontal 
from the parietal lobe. 

3. The parietal fissure , arising a short distance behind the fissure of 
Rolando, upon the convexity of the hemisphere, runs downward and back¬ 
ward to its posterior extremity. 

4. The parieto-occipitalfissure , separating the occipital from the parietal 
lobes. Beginning upon the outer surface of the cerebrum, it is continued 
on the mesial aspect downward and forward until it terminates in the calca¬ 
rine fissure. 

5. The calios O' marginal fissure lying upon the mesial surface, where it 
runs parallel with the corpus callosum. 

Secondary fissures of importance are found in different lobes of the 
cerebrum, separating the various convolutions. In the anterior lobe are 
found the pre-central , superior frontal , and inferior frontal fissures; in 
the temporo-sphenoidal lobes are found the first and second temporo- 
sphenoidal fissures ; in the occipital lobe, the calcarine and. hippo-campal 
fissures. 

Convolutions. Frontal lobe. 

The ascending frontal convolution , situated in front of the fissure of 
Rolando, runs downward and forward; it is continuous above with the 
anterior frontal, and below with the inferior frontal convolution. 

The superior frontal convolution is bounded internally by the longitu¬ 
dinal fissure, and externally by the superior frontal fissure; it is connected 
with the superior end of the frontal convolution, and runs downward and 
forward to the anterior extremity of the frontal lobe, where it turns back¬ 
ward, and rests upon the orbital plate of the frontal bone. 

The middle frontal convolution , the largest of the three, runs from behind 
forward, along the sides of the lobe, to its anterior part; it is bounded above 
by the superior and below by the inferior frontal fissures. 


CEREBRUM. 


175 


The inferior frontal convolution winds around the ascending branch of 
the fissure of Sylvius, in the anterior and inferior portion of the cerebrum. 

* Parietal Lobe.— ihe ascending parietal convolution is situated just 
behind the fissure of Rolando, running downward and forward; above, it 
becomes continuous with the upper parietal convolution, and below, winds 
around to be united with the ascending frontal. 


Fig. 18. 

f' 



DIAGRAM SHOWING FISSURES AND CONVOLUTIONS OF THE LEFT SIDE OF THE HUMAN 

BRAIN. 

F. Frontal. P. Parietal. O. Occipital. T. Temporo-sphenoidal lobe. S. Fissure 
of Sylvius. S'. Horizontal. S". Ascending ramus of S. c. Sulcus centralis, or 
fissure of Rolando. A. Ascending frontal, and B. ascending parietal, convolution. 
Fj. Superior. F 2 . Middle, and F 3 . Inferior frontal convolutions, fi. Superior, 
f 2 . Inferior, frontal fissures. f 3 . Sulcus praecentralis. P. Superior parietal lobule. 
P 2 . Inferior parietal lobule, consisting of P 2 , supra-marginal gyrus, and P' 2 , angular 
gyrus, ip. Sulcus interparietalis. c m. Termination of calloso-marginal fissure. 
Oi. First, 0 2 , second, 0 3 , third, occipital convolutions, p o. Parieto-occipital 
fissure, o. .Transverse occipital fissure. *? 2 Inferior longitudinal occipital fissure. 
Tj, first. To, second, T 3 , temporo-sphenoidal, convolutions. t\, first, / 2 , second, 
temporo-sphenoidal fissures.— Landois’ Physiology. 

















176 


HUMAN PHYSIOLOGY. 


The upper parietal convolution is situated between the parietal and 
longitudinal fissures. 

The supra-?narginal convolution winds around the superior extremity 
of the fissure of Sylvius. 

The angular convolution , a continuation of the preceding, follows the 
parietal fissure to its posterior extremity, and then makes a sharp angle 
downward and forward. 

Temporo-sphenoidal Lobe.—Contains three well marked convolu¬ 
tions, the superior , middle , and inferior , separated by well-defined fissures, 
and continuous posteriorly with the convolutions of the parietal lobe. 

The Occipital Lobe lies behind the parieto-occipital fissure, and con¬ 
tains the superior , middle , and infeHor convolutions, not well marked. 

The central lobe , or island of Reil , situated at the bifurcation of the 
fissure of Sylvius, is a triangular-shaped cluster of six convolutions, the 
gyri operti, which are connected with those of the frontal, parietal, and 
temporo-sphenoidal lobes. 

Upon the inner or mesial aspect of the hemisphere are found (Fig. 15)— 

1. The paracentral lobule , lying in the region of the upper extremity of 
the fissure of Rolando; it contains the large giant cells of Betz. Injury 
to this convolution is followed by degeneration of the motor tract. 

2. The gyrus fornicatus , lying below the calloso-marginal fissure. 
Running parallel with the corpus callosum, it terminates at its posterior 
border in the hippocampal gyrus. 

3. The gyrus hippocampus (H) is formed by the union of the preceding 
convolution with the occipito-temporal. It runs forward and terminates in 
a hooked extremity— uncus. 

4. The quadrate lobule or precuneus lies between the upper extremity 
of the calloso-marginal fissure and the parieto-occipital. 

5. The cuneus lies posteriorly to the quadrate lobule. It is a wedge- 
shaped mass enclosed by the calcarine and parieto-occipital fissures. 

Structure. The gray matter of the cerebrum, about one-eighth of an 
inch thick, is composed of five layers of nerve cells : (1) a superficial layer, 
containing a few small multipolar ganglion cells; (2) small ganglion cells, 
pyramidal in shape; (3) a layer of large pyramidal ganglion cells with 
processes running off superiorly and laterally; (4) the granular formation 
containing nerve cells; (5) spindle-shaped and branching nerve cells of 
moderate size. 

The white matter consists of three distinct sets of fibers :_ 

1. The diverging ox pedimcular fibers are mainly derived from the 


CEREBRUM. 


177 


columns of the cord and medulla oblongata; passing upward through the 
crura cerebri, they receive accessory fibers from the olivary fasciculus, cor¬ 
pora quadrigemina, and cerebellum. Some of the fibers terminate in the 
optic thalami and corpora striata, while others radiate into the the anterior, 
middle, and posterior lobes of the cerebrum. 

2. The transverse commisstiral fibers connect together the two hemi¬ 
spheres, through the corpus callosum and anterior and posterior commis¬ 
sures. 


3. The longitudinal commissural fibers connect together different parts 
of the same hemisphere. 

Fig. 19. 



DIAGRAM SHOWING FISSURES AND CONVOLUTIONS ON MESIAL ASPECT OF THE RIGHT 

HEMISPHERE. 

Median aspect of the right hemisphere. CC, corpus callosum divided longitudinally; 
Gf,gyrus fornicatus; H, gyrus hippocampi; h, sulcus hippocampi; U, uncinate 
gyrus ; cm, calloso-marginal fissure ; F, first frontal convolution ; c, terminal por¬ 
tion of fissure of Rolando; A, ascending frontal; B, ascending parietal convolution 
and paracentral lobule ; P^, precuneus or quadrate lobule ; Oz, cuneus ; Po, parie- 
to-occipital fissure; 0\, transverse occipital fissure ; oc, calcarine fissure ; oc' , super¬ 
ior, oc", inferior, ramus of the same ; D, gyrus descendens ; T 4 , gyrus occipito-tem- 
poralis lateralis (lobulus fusiformis); T 5 , gyrus occipito-temporalis medialis (lobulus 
lingttalis). 

Functions.—The cerebral hemispheres are the centers of the nervous 
system through which are manifested all the phenomena of the mind; 
they are the centers in which impressions are registered, and reproduced 
subsequently as ideas ; they are the seat of intelligence, reason, and will. 











Fig. 20, 



The figures are constructed by marking on the brain ofi man, in their respective 

situations, the areas ofi the brain ofi the monkey as determined by experiment, and 

the description ofi the effects ofi stimulating the variotis areas refiers to the brain of 

the monkey. 

(1) Advance of the opposite hind limb, as in walking. 

(2) , (3), (4) Complex movements of the opposite leg and arm, and of the trunk, as in 
swimming. 

(а) , (b), (c), ( d ) Individual and combined movements of the fingers and wrist of the 
opposite hand. Prehensile movements. 

(5) Extension forward of the opposite arm and hand. 

(б) Supination and flexion of the opposite forearm. 

(7) Retraction and elevation of the opposite angle of the mouth, by means of the zygo¬ 
matic muscles. 

(8) Elevation of the ala nasi and upper lip, with depression of the lower lip on the oppo¬ 
site side. 

(9) , (10) Opening of the mouth, with (9) protrusion and (10) retraction of the tongue ; 
region of aphasia, bilateral action. 

( 11 ) Retraction of the opposite angle of the mouth, the head turned slightly to one side. 

(12) The eyes open widely, the pupils dilate, and the head and eyes turn toward the 
opposite side. 

(13) , (13') The eyes move toward the opposite side with an upward (13) or downward 
(13') deviation. The pupils are generally contracted. 

(14) Pricking of the opposite ear, the head and eyes turn to the opposite side, and the 
pupils dilate largely. 


SIDE VIEW OF THE BRAIN OF MAN, WITH THE AREAS OF THE CEREBRAL CONVOLU 

TIONS ACCORDING TO FERRIER. 


178 










CEREBRUM. 


179 


However important a center the cerebrum may be, for the exhibition of 
this highest form of nervous action, it is not directly essential for the con¬ 
tinuance of life, for it does not exert any control over those automatic 
reflex acts, such as respiration, circulation, etc., which regulate the functions 
of organic life. 

From the study of comparative anatomy, pathology, vivisection, etc., 
evidence has been obtained which throws some light upon the physiology 
of the cerebral hemispheres. 

1. Comparative anatomy shows that there is a general connection be¬ 
tween the size of the brain, its texture, the depth and number of convolu¬ 
tions, and the exhibition of mental power. Throughout the entire animal 
series, the increase in intelligence goes hand in hand with an increase in 
the development of the brain. In man there is an enormous increase in 
size over that of the highest animals, the anthropoids. The most cultivated 
races of men have the greatest cranial capacity ; that of the educated 
European being about 116 cubic inches, that of the Australian being about 
60 cubic inches, a difference of 56 cubic inches. Men distinguished for 
great mental power usually have large and well-developed brains; that of 
Cuvier weighed 64 ozs.; that of Abercrombie 63 ozs.; the average being 
about 48 to 50 ozs.; not only the size, but, above all, the texture of the 
brain, must be taken into consideration. 

2. Pathology .—Any severe injury or disease disorganizing the hemi¬ 
spheres is at once attended by a disturbance, or entire suspension, of mental 
activity. A blow on the head producing concussion, or undue pressure 
from cerebral hemorrhage, destroys consciousness; physical and chemical 
alterations in the gray matter have been shown to coexist with insanity, 
loss of memory, speech, etc. Congenital defects of organization from im¬ 
perfect development are usually accompanied by a corresponding deficiency 
of intellectual power and the higher instincts. Under these circumstances 
no great advance in mental development can be possible, and the intelli¬ 
gence remains at a low grade. In congenital idiocy not only is the brain 
of small size, but it is wanting in proper chemical composition, phosphorus, 
a characteristic ingredient of the nervous tissue, being largely diminished 
in amount. 

3. Experimentation upon the lower animals by removing the cerebral 
hemispheres is attended by results similar to those observed in disease and 
injury. Removal of the cerebrum in pigeons produces complete abolition 
of intelligence, and destroys the capability of performing spontaneous move¬ 
ments. The pigeon remains in a condition of profound stupor, which is 
not accompanied, however, by a loss of sensation, or of the power of pro- 


180 


HUMAN PHYSIOLOGY. 


ducing reflex or instinctive movements. The pigeon can be temporarily 
aroused by pinching the feet, loud noises, light placed before the eyes, etc., 
but soon relapses into a state of quietude, being unable to remember im¬ 
pressions and connect them with any train of ideas, the faculties of memory, 
reason, and judgment being completely abolished. 


CEREBRAL LOCALIZATION OF FUNCTION. 

From experiments made upon animals, and the results of clinical and 
post-mortem observations upon men, it has been shown that the phenomena 
of organic and psychical life are presided over by anatomically localized 
centers in the brain. A knowledge of the position of these centers 
becomes of the highest importance in localizing the seat of lesions, 
thrombi, hemorrhages, new growths, etc., which show themselves in 
paralysis, epilepsies, etc. It has not been possible to thus localize all 
functions, and to many parts of the brain no special use can be assigned. 
The following are the centers most definitely mapped out and that are of 
paramount importance:— 

Motor Centers.—These are in the cortical gray matter, and are arranged 
along either side of the fissure of Rolando. This area is known as the 
motor area or motor zone , stimulation of which is followed by convulsive 
movements of the muscles of the opposite side of the body, while destruc¬ 
tion of the gray matter of this area is followed by permanent paralysis of 
the muscles of the opposite side. From experiments made upon monkeys 
Ferrier has mapped out a number of motor centers which he has transferred 
to corresponding localities on the human brain (see Fig. 16). The descrip¬ 
tive test of the figure renders his results intelligible. Pathological studies 
have largely confirmed his deductions. In a general way it may be said 
that the upper third of the ascending frontal and parietal convolutions 
about this fissure preside over the movements of the leg of the opposite side 
of the body; the middle third controls the movements of the arm; the 
upper part of the inferior third is the facial area. The lowest part of the 
inferior third governs the motility of the lips and tongue, and this space, 
with the posterior extremity of the third frontal convolution, constitutes the 
speech center. 

The experiments of Horsley and Schafer have enabled them to furnish 
a new diagrammatic representation of the motor area and to more accurately 
define the special areas upon the lateral and mesial aspects of the brain of 
the monkey. The boundaries of the general and special areas as deter- 


CEREBRAL LOCALIZATION OF FUNCTION. 


181 


mined by these observers will be readily understood by an examination of 
Figs. 21 and 22. 

For diagnostic purposes the motor areas for the face and limbs have been 
subdivided as follows :— 

1. The face area may be divided into an upper part comprising about 
one-third, and a lower part comprising the remaining two-thirds. In the 
upper part are centers governing the movements of the muscles of the oppo¬ 
site angle of the mouth and of the lower face. The anterior portion of the 
lower two-thirds controls the movements of the vocal cords and may be 
regarded as a laryngeal center; the posterior portion governs the opening 
and shutting'of the mouth and the protrusion and retraction of the tongue. 

2. The upper limb area may be subdivided as follows: The upper part 


Fig. 21. 



DIAGRAM OF THE MOTOR AREAS ON THE OUTER SURFACE OF A MONKEY’S BRAIN. 

—Horsley and Schafer. 

controls the movements of the shoulder; posterior and below this point are 
centers for the elbow; below and anteriorly, centers for the wrist and finger 
movements, while lowest and posteriorly centers governing the thumb. 

3. The leg area may be subdivided as follows: The anterior part, both 
on the mesial and lateral surfaces, contains centers governing the hip and 
thigh movements; in the posterior part are centers for the movements of 
the leg and toes. The center for the big toe has been located in the para¬ 
central lobule. 

4. The trunk area , situated largely on the mesial surface, contains 
anteriorly centers governing the rotation and arching of the spine, while 
posteriorly are found centers governing movements of the tail and pelvis. 

5. The head area , or area for visual direction , contains centers excita- 


182 


HUMAN PHYSIOLOGY. 


tion of which causes “ opening of the eyes, dilatation of the pupils, and 
turning of the head to the opposite side, with conjugate deviation of the 
eyes to that side.” 

The centers of origin of the nerves for the ocular muscles lie in the gray 
matter of the aqueduct of Sylvius. Destruction of the gray matter at these 
points is followed by paralysis of the muscles of the opposite side of the 
body, and morbid growths, hemorrhages, or thrombi of the vessels of the 
parts result in abnormal stimulation or interference of the functions corre¬ 
sponding to the nature and extent of the lesion. Cerebral or Jacksonian 
epilepsy is a result of local cortical disease. 

Center for Speech. Pathological investigations have demonstrated that 
the left third frontal convolution is of essential importance for speech. 

Fig. 22. 


DIAGRAM OF THE MOTOR AREAS ON THE MARGINAL CONVOLUTION OF A MONKEY’S 
brain.— Horsley and Schafer. 

Adjoining this convolution are the centers controlling the motility of the 
lips, tongue, etc. In the majority of the cases the speech centers are on the 
left side of the brain, though in exceptional cases it is on the right side, 
especially in left-handed people. In deaf-mutes this convolution is very 
imperfectly developed, while in monkeys it is quite rudimentary. 

Lesions of the third frontal convolution on the left side, if the patient be 
right-handed, produce the various forms of aphasia or the partial or com¬ 
plete loss of the power of articulate speech. 

Aphasia is of many degrees and kinds. In ataxic aphasia the patient is 
unable to communicate his thoughts by words, there being an inability to 
execute the movements of the mouth, etc., necessary for speech. In 







CEREBRAL LOCALIZATION OF FUNCTION. 


183 



agraphic aphasia there is an inability to execute the movements necessary 
for writing, though the mental processes are retained. In the ataxic form 
the lesion is in the 3d frontal convolution, and in the agraphic form it is in 
the arm center. 

In amnesic aphasia there is a loss of the memory of words, the purest 
examples of which consist of the affections known as word deafness and 
word blindness. In word deafness the patient cannot understand vocal 
speech, though he is capable of hearing other sounds. This condition is 
associated with lesion of the first temporal convolution. In word blindness 
the patient cannot name a 

letter or a word when Fig ' 23 * 

printed or written, though 
he can see all other objects. 

This condition is associated 
with impairment of the visual 
centers. 

Figure 23 will illustrate 
the conditions in the various 
forms of aphasia. Impres¬ 
sions are constantly passing 
from eye and ear to the 
visual and auditory centers 
and there registered. Com¬ 
missural fibers connect these 
centers with the arm and 
speech centers, which in turn 
are connected by efferent 
fibers with the muscles of 
the hand and vocal appa¬ 
ratus. Muscular movements 
of the eyes, hand, and mouth 
are also registered by means 
of the afferent fibers, s, s / ,s // . 

Sensory Centers. 

These are the centers in 
which the sensory impres¬ 
sions are coordinated, and 

in which they probably become parts of our consciousness. The most im* 
portant are:— 

The visual center , located in the occipital lobe and especially in the 








184 


HUMAN PHYSIOLOGY. 


cuneus. Unilateral destruction of this area results in hemianopsia , or 
blindness of the corresponding halves of the two retinae. Destruction of 
both occipital lobes in man results in total blindness. Stimulation or irri¬ 
tation of the visual center causes photopsia , or hallucinations of sight, in 
corresponding halves of the retinae. There have been instances of injury of 
these parts when sensations of color were abolished with preservation of 
those of space and light, thus showing a special localization of the color 
center. Late experiments show that the centers of the two hemispheres are 
united, as ocular fatigue of a non-used eye was proportional to the fatigue 
of the exercised one. 

The auditory centers are located in the temporo-sphenoidal lobes. Word 
deafness is associated with softening of these parts, and their complete re¬ 
moval results in deafness. 

The gustatory and olfactory centers are located in the uncinate gyrus, 
on the inner side of the temporo-sphenoidal lobes. There does not seem to 
be any differentiation, up to this time, of these two centers. 

The center for tactile impressions was located by Ferrier in the hippo¬ 
campal region. Horsley and Schafer found that destructive lesions of the 
gyrus fornicatus was followed by hemianesthesia of the opposite side of the 
body, which was more or less marked and persistent. These observers 
conclude that the limbic lobe “ is largely, if not exclusively, concerned in 
the appreciation of sensations painful and tactile.” 

The superior' and middle frontal convolutions appear to be the seat of 
the reason, intelligence, and will. Destruction of these parts is fol¬ 
lowed by proportional hebetude, without any impairment of sensation or 
motion. 

SYMPATHETIC NERVOUS SYSTEM. 

The Sympathetic Nervous System consists of a chain of ganglia 
connected together by longitudinal nerve filaments, situated on each side of 
the spinal column, running from above downward. The two ganglionic 
cords are connected together in the interior of the cranium by the ganglion 
of Ribes, on the anterior communicating artery, and terminate in the gan¬ 
glion impar, situated at the top of the coccyx. 

The chain of ganglia is divided into groups, and named according to the 
location in which they are found, viz., cranial , four in number; cervical , 
three; thoracic , twelve; lumbar , five ; sacral , five ; coccygeal , one. Each 
ganglion consists of a collection of vesicular nervous matter, bundles of 
non-medullated nerve fibers, imbedded in a capsule of connective tissue. 


SYMPATHETIC NERVOUS SYSTEM. 


185 


The ganglia are reinforced by motor and sensory fibers from the cerebro¬ 
spinal nervous system. 

The Ganglia have distinet nerve fibers from which branches are dis¬ 
tributed to the glands, arteries, muscles, and to the cerebral and spinal 
nerves; many pass, also, to the visceral ganglia, e.g., cardiac, semilunar, 
pelvic, etc. 

Cephalic Ganglia. 

1. The ophthalmic or ciliary ganglion is situated in the orbital cavity 
posterior tp the eyeball; it is of small size and of a reddish-gray color; 
receives filaments of communication from the motor oculi, ophthalmic 
branch of the fifth pair, and the carotid plexus. Its filaments of distribution 
are the ciliary nerves, which consist of— 

1. Motor fibers for the circular fibers of the iris and ciliary muscle. 

2. Sensory fibers for the cornea, iris, and associated parts. 

3. Vasomotor fibers for the blood-vessels of the choroid, iris, and 
retina. 

4. Motor fibers for the dilator fibers of the iris. 

2. The spheno-palatine, or Meckel’s ganglion, triangular in shape, is 
situated in the spheno maxillary fossa; receives filaments from the facial 
(Vidian nerve), and the superior maxillary branch of the fifth nerve. Its 
filaments of distribution pass to the gums, the soft palate, levator pal at i, and 
azygos uvulae muscles. 

3. The otic , or Arnold’s ganglion, is of small size, oval in shape, and 
situated beneath the foramen ovale; receives a motor filament from the 
facial and sensory filaments from the glosso-pharyngeal and fifth nerve; 
sends filaments to the mucous membrane of the tympanic cavity and to the 
tensor tympani muscle. 

4. The submaxillary ganglion, situated in the submaxillary gland, 
receives filaments from the chorda tympani, sensory filaments from the lin¬ 
gual branch of the fifth nerve, and filaments from the sympathetic. The 
chorda tympani nerve supplies vaso-dilator and secretory fibers to the sub¬ 
maxillary and sub-lingual glands. The fifih nerve endows the glands with 
sensibility, while the sympathetic supplies secretory or tropic fibers. 

Cervical Ganglia. 

The superior cervical ganglion is fusiform in shape, of a grayish-red 
color, and situate opposite the second and third cervical vertebrse; it sends 
branches to form the carotid and cavernous plexuses which follow the 
course of the carotid arteries to their distribution; also sends branches to 
M 


186 


HUMAN PHYSIOLOGY. 


join the glosso-pharyngeal and pneumogastric, to form the pharyngeal 
plexus. 

The middle cervical ganglion, the smallest of the three, is occasionally 
wanting; it is situated opposite the fifth cervical vertebra; sends branches 
to the superior and inferior cervical ganglion and to the thyroid artery. 

The inferior cervical ganglion, irregular in form, is situated opposite the 
last cervical vertebra ; it is frequently fused with the first thoracic ganglion. 

The superior , middle , and inferior cardiac nerves , arising from these 
cervical ganglia, pass downward and forward to form the deep and super¬ 
ficial cardiac plexuses located at the bifurcation of the trachea, from which 
branches are distributed to the heart, coronary arteries, etc. 

The Thoracic Ganglia are usually twelve in number, placed against 
the heads of the ribs behind the pleura; they are small in size and gray in 
color; they communicate with the cerebro-spinal nerves by two filaments, 
one of which is white, the other gray. 

The great splanchnic nerve is formed by the union of branches from the 
sixth, seventh, eight, and ninth ganglia; it passes through the diaphragm 
to the semilunar ganglion. 

The lesser splanchnic nerve is formed by the union of filaments from the 
tenth and eleventh ganglia, and is distributed to the celiac plexus. 

The renal splanchnic nerve arises from the last thoracic ganglion and 
terminates in the renal plexus. 

The semilunar ganglia , the largest of the sympathetic, are situated by 
the side of the celiac axis; they send radiating branches to form the solar 
plexus; from the various plexuses, nerves follow the gastric, splenic, hep¬ 
atic, renal, etc., arteries, into the different abdominal viscera. 

The Lumbar Ganglia, four in number, are placed upon the bodies of 
the vertebra; they give off branches which unite to form the aortic lumbar 
plexus and the hypogastric plexus, and follow the blood-vessels to their 
terminations. 

The Sacral and Coccygeal Ganglia send filaments of distribution to 
all the blood-vessels of the pelvic viscera. 

Properties and Functions.—The sympathetic nerve possesses both 
sensibility and the power of exciting motion, but these properties are much 
less decided than in the cerebro-spinal system. Irritation of the ganglia 
does not produce any evidence of pain until some time has elapsed. If 
caustic soda be applied to the semilunar ganglia, or a galvanic current be 
passed through the splanchnic nerves, no instantaneous effect is noticed, as 
in the case of the cerebro-spinal nerves; but in the course of a few seconds 


SYMPATHETIC NERVOUS SYSTEM. 


187 


a slow, progressive contraction of the muscular coat of the intestines is 
established, which continues for some time after the irritation is removed. 
Division of the sympathetic nerve in the neck is followed by a vascular 
congestion of the parts above the section on the corresponding side, attended 
by an increase in the temperature; not only is there an increase in the 
amount of blood, but the rapidity of the blood current is very much has¬ 
tened and the blood in the veins becomes of a brighter color. Galvaniza¬ 
tion of the upper end of the divided nerve causes all of the preceding 
phenomena to disappear; the congestion decreases, the temperature falls, 
and the venous blood becomes dark again. 

The sympathetic exerts a similar influence upon the circulation of the 
limbs and the glandular organs ; destruction of the first thoracic ganglion 
and division of the nerves forming the lumbar and sacral plexuses is fol¬ 
lowed by a dilatation of the vessels, an increased rapidity of the circulation, 
and an elevation of temperature in the anterior and posterior limbs ; gal¬ 
vanization of the peripheral ends of these nerves causes all of these phe¬ 
nomena to disappear. Division of the splanchnic nerve causes a dilatation 
of the blood-vessels of the intestine. 

These phenomena of the sympathetic nerve system are dependent upon 
the presence of vasomotor nerves, which, under normal circumstances, 
exert a tonic influence upon the blood-vessels. These nerves, derived 
from the cerebro-spinal system, the medulla oblongata, leave the spinal 
cord by the rami communicantes , enter the sympathetic ganglia, and 
finally terminate in the muscular wall of the blood-vessels. 

Sleep is a periodical condition of the nervous system, in which there is 
a partial or complete cessation of the activities of the higher nerve centers. 
The cause of sleep is a diminution in the quantity of blood, occasioned by a 
contraction of the smaller arteries under the influence of the vasomotor 
nerves. 

During the waking state the brain undergoes a physiological waste, as 
a result of the exercise of its functions; after a certain length of time its 
activities become enfeebled, and a period of repose ensues, during which a 
regeneration of its substance takes place. 

When the brain becomes enfeebled there is a diminished molecular 
activity and an accumulation of waste products ; under these circumstances 
it ceases to dominate the medulla oblongata and the spinal cord. These 
centers then act more vigorously, and diminish the caliber of the cerebral 
blood-vessels through the action of the vasomotor nerves, producing a con¬ 
dition of physiological anemia and sleep; during this state waste products 
are removed, force is stored up, nutrition is restored, and waking finally 


occurs. 


188 


HUMAN PHYSIOLOGY. 


THE SENSE OF TOUCH. 

The Sense of Touch is a modification of general sensibility, and 
located in the skin, which is especially adapted for this purpose, on account 
of the number of nerves and papillary elevations it possesses. The structures 
of the skin and the modes of termination of the sensory nerves have already 
been considered. 

The Tactile Sensibility varies in acuteness in different portions of the 
body, being most marked in those regions in which the tactile corpuscles 
are most abundant, e.g ., the palmar surface of the third phalanges of the 
fingers and thumb. 

The relative sensibility of different portions of the body has been ascer¬ 
tained by means of a pair of compasses, the points of which are guarded by 
cork, and then determining how clcsely they could be brought together, and 
yet be felt at two distinct points. The following are some of the measure¬ 
ments :— 


Point of tongue,. 

Palmar surface of third phalanx, 

Red surface of lips,. 

Palmar surface of metacarpus, . 

Tip of the nose,. 

Part of lips covered by skin, 

Palm of hand, . 

Lower part of forehead, .... 

Back of hand,. 

Dorsum of foot,.• 

Middle of the thigh,. 


^ of a line. 
. I line. 

. 2 lines. 


• 3 “ 

• 4 “ 

• 5 “ 

io “ 
14 “ 

18 “ 
30 “ 


The sense of touch communicates to the mind the idea of resistance only, 
and the varying degrees of resistance offered to the sensory nerves enable 
us to estimate, with the aid of the muscular sense, the qualities of hardness 
and softness of external objects. The idea of space or extension is obtained 
when the sensory surface or the external object changes its place in regard 
to the other ; the character of the surface, its roughness or smoothness , is 
estimated by the impressions made upon the tactile papillse. 

Appreciation of Temperature. —The general surface of the body is more 
or less sensitive to differences of temperature, though this sensation is 
separate from that of touch; whether there are nerves especially adapted 
for the conduction of this sensation has not been fully determined. Under 
pathological conditions, however, the sense of touch may be abolished, 
while the appreciation of changes in temperature may remain normal. 













THE SENSE OF TASTE. 


189 


The cutaneous surface varies in its sensibility to temperature in different 
parts of the body, and depends, to some extent, upon the thickness of the 
skin, exposure, habit, etc.; the inner surface of the elbow is more sensitive 
to changes in temperature than the outer portion of the arm ; the left hand 
is more sensitive than the right; the mucous membrane, less so than the 
skin. 

Excessive heat or cold has the same effect upon the sensibility; the tem¬ 
peratures most readily appreciated are those between 5o p F. and 115 0 F. 

The sensations of pain and tickling appear to be conducted to the brain, 
also, by nerves different from those of touch; in abnormal conditions the 
appreciation of pain may be entirely lost, while touch remains unimpaired. 


THE SENSE OF TASTE. 

The Sense of Taste is localized mainly in the mucous membrane 
covering the superior surface of the tongue. 

The Tongue is situated in the floor of the mouth ; its base is directed 
backward, and connected with the hyoid bone, by numerous muscles, with 
the epiglottis and soft palate ; its apex is directed forward against the pos¬ 
terior surface of the teeth. 

The substance of the tongue is made up of intrinsic muscular fibers, the 
linguales ; it is attached to surrounding parts, and its various movements 
performed by the extrinsic muscles, e.g stylo-glossus, genio-hyo-glossus, 
etc. 

The mucous membrane covering the tongue is continuous with that lining 
the commencement of the alimentary canal, and is furnished with vascular 
and nervous papillae. 

Th z papillce are analogous in their structure to those of the skin, and are 
distributed over the dorsum of the tongue, giving it its characteristic rough¬ 
ness. 

There are three principal varieties :— 

1. The filiform papillce are most numerous, and cover the anterior two- 
thirds of the tongue; they are conical or filiform in shape, often prolonged 
into filamentous tufts, of a whitish color, and covered by horny epithelium. 

2. The fungiform papillce are found chiefly at the tip and sides of the 
tongue ; they are larger than the preceding, and may be recognized by 
their deep red color. 

3. The circumvallatepapillce are rounded eminences, from eight to ten 
in number, situated at the base of the tongue, where they form a V-shaped 


190 


HUMAN PHYSIOLOGY. 


figure. They are quite large, and consist of a central projection of mucous 
membrane, surrounded by a wall, or circumvallation, from which they de¬ 
rive their name. 

The Taste Beakers, supposed to be the true organs of taste, are flask¬ 
like bodies, ovoid in form, about of an inch in length, situated in the 
epithelial covering of the mucous membrane, on the circumvallate papillse. 
They consist of a number of fusiform, narrow cells, and curved so as to 
form the walls of this flask-like body; in the interior are elongated cells, 
with large, clear nuclei, the taste cells. 

Nerves of Taste.—The chorda tympani nerve, a branch of the facial, 
after leaving the cavity of the tympanum, joins the third division of the fifth 
nerve between the two pterygoid muscles, and then passes forward in the 
lingual branches, to be distributed to the mucous membrane of the anterior 
two-thirds of the tongue. Division or disease of this nerve is followed by 
a loss of-taste in the part to which it is distributed. 

The glossopharyngeal enters the tongue at the posterior border of the 
hyo-glossus muscle, and is distributed to the mucous membrane of the base 
and sides of the tongue, fauces, etc. 

The lingual branch of the trifacial nerve endows the tongue with gen¬ 
eral sensibility ; the hypoglossal endows it with motion. 

The nerves of taste in the superficial layer of the mucous membrane 
form a fine plexus, from which branches pass to the epithelium and pene¬ 
trate it; others enter the taste beakers, and are directly connected with the 
taste cells. 

The seat of the sense of taste has been shown by experiment to be the 
whole of the mucous membrane over the dorsum of the tongue, soft palate, 
fauces, and upper part of the pharynx. 

The Sense of Taste enables us to distinguish the savor of substances 
introduced into the mouth, which is different from tactile sensibility. The 
sapid quality of substances appreciated by the tongue are designated as 
bitter, sweet, alkaline, sour, salt, etc. 

The Essential Conditions for the production of the impressions of 
taste are (i) a state of solubility of the food; (2) a free secretion of the 
saliva, and (3) active movements on the part of the tongue, exciting pres¬ 
sure against the roof of the mouth, gums, etc., thus aiding the solution of 
various articles and their osmosis into the lingual papillse. Sapid substances, 
when in a state of solution, pass into the interior of the taste beakers, and 
come into contact, through the medium of the taste cells, with the terminal 
filaments of the gustatory nerves. 


THE SENSES OF SMELL AND SIGHT. 


191 


THE SENSE OF SMELL. 

The Sense of Smell is located in the mucous membrane lining the 
upper part of the nasal cavity, in which the olfactory nerves are distributed. 

The Nasal Fossae are two cavities, irregular in shape, separated by 
the vomer, the perpendicular plate of the ethmoid bone, and the triangular 
cartilage. They open anteriorly and posteriorly by the anterior and pos¬ 
terior nares, the latter communicating with the pharynx; They are lined 
by mucous membrane, of which the only portion capable of receiving 
odorous impressions is the part lining the upper one-third of the fossae. 

The Olfactory Nerves, arising by three roots from the posterior and 
inferior surface of the anterior lobes, pass forward to the cribriform plate 
of the ethmoid bone, where they each expand into an oblong body, the 
olfactory bulb. From its under surface from fifteen to twenty filaments 
pass downward through the foramina, to be distributed to the olfactory 
mucous membrane, where they terminate in long, delicate, spindle-shaped 
cells, the olfactory cells, situated between the ordinary epithelial cells. 

The olfactory bulbs are the centers in which odorous impressions are 
perceived as sensations, destruction of these bulbs being attended by an 
abolition of the sense of smell. 

In animals which possess an acute sense of smell there is a corresponding 
increase in the development of the olfactory bulbs. 

The Essential Conditions for the sense of smell are (i) a special 
nerve center capable of receiving impressions and transforming them into 
odorous sensations. (2) Emanations from bodies which are in a gaseous 
or vaporous condition. (3) The odorous emanations must be drawn freely 
through the nasal fossae; if the odor be very faint, a peculiar inspiratory 
movement is made, by which the air is forcibly brought into contact with 
the olfactory filaments. The secretions of the nasal fossae probably dis¬ 
solve the odorous particles. 

Various substances, as ammonia, horseradish, etc., excite the sensibility 
of the mucous membrane, which must be distinguished from the perception 
of true odors. 


THE SENSE OF SIGHT. 

The Eyeball.—The eyeball, or organ of vision, is situated at the fore 
part of the orbital cavity and supported by a cushion of fat; it is protected 
from injury by the bony walls of the cavity, the lids and lashes, and is so 


192 


HUMAN PHYSIOLOGY. 


situated as to permit of an extensive range of vision. The eyeball is loosely 
held in position by a fibrous membrane, the capsule of Tenon, which is 
attached on the one hand to the eyeball itself and on the other to the walls 
of the cavity. Thus suspended, the eyeball is capable of being moved in 
any direction by the contraction of the muscles attached to it. 

Structure.—The eyeball is spheroidal in shape and measures about nine- 
tenths of an inch in its antero-posterior diameter, and a little less in its 
transverse diameter. When viewed in profile it is seen to consist of the 
segments of two spheres, of which the posterior is the larger, occupying 
five-sixths, and the anterior the smaller, occupying one-sixth of the ball. 

The eye is made up of several membranes concentrically arranged, within 
which are enclosed the refracting media essential to vision. These mem¬ 
branes, enumerated from without inward, are: 1st, the sclerotic and cornea; 
2d, the choroid and iris; 3d, the retina; the refracting media are the 
aqueous humor, the crystalline lens, and vitreous humor. 

The Sclerotic and Cornea—The sclerotic is the opaque fibrous mem¬ 
brane covering the posterior five-sixths of the ball. It is composed of con¬ 
nective tissue arranged in layers which run both transversely and longitudi¬ 
nally ; it is pierced posteriorly by the optic nerve about one-tenth of an 
inch internal to the optic axis. The sclerotic by its density gives form to 
the eye and protects the delicate structures within it, and serves for the 
attachment of the muscles by which the ball is moved. 

The cornea is a transparent non-vascular membrane covering the anterior 
one-sixth of the eyeball. It is nearly circular in shape and is continuous at 
the circumference with the sclerotic, from which it cannot be separated. 
The substance of the cornea is made up of thin layers of delicate, trans¬ 
parent fibrils of connective tissue more or less united together; between 
these layers are found a number of inter-communicating lymph spaces lined 
by endothelium, which are in connection with lymphatics. Leucocytes or 
lymph corpuscles are often found in these spaces. The anterior surface of 
the cornea is covered by several layers of nucleated epithelium which rest 
upon a structureless membrane known as the anterior elastic lamina. The 
posterior surface is covered by a similar membrane, the membrane of 
Descemet, which becomes continuous at its periphery with the iris; it is also 
covered by a layer of epithelial cells. At the junction of the cornea and 
sclerotic is found a circular groove, the canal of Scklemm. 

The Choroid, the Iris, the Ciliary Muscle, and Ciliary processes 
together constitute the second or middle coat of the eyeball. 

The choroid is a dark-brown membrane which extends forward nearly 


THE SENSE OF SIGHT. 


193 


to the cornea, where it terminates in a series of folds, the ciliary processes. 
Tn its structure the choroid is highly vascular, consisting of both arteries and 
veins. Externally it is connected with the sclerotic by connective tissue; 
internally it is lined by a layer of hexagonal pigment cells which, though 
usually classed as belonging to the choroid, is now known to belong, em- 
bryologically and physiologically, to the retina. From without inward may 
be distinguished the following layers :— 

1. The lamina supra choroidea. 

2. The elastic layer of Sattler, consisting of two endothelial layers. 

3. The chorio-capillaris, choroid proper, or membrane of Ruysch, a 

thick, elastic network of arterioles and capillaries lying within the 
outer layer of veins and arteries called the vena vorticosse. 

4. The lamina vitrea or internal limiting membrane. 

The choroid with its contained blood-vessels bears an important relation 
to the nutrition of the eye ; it provides for the blood supply, for drainage from 
the body of the eye, and presents an uniform and high temperature to the 
retina. 

The iris is the circular variously-colored membrane placed in the an¬ 
terior portion of the eye just behind the cornea. It is perforated a little to 
the nasal side of the center by a circular opening, the pupil. The outer 
or circumferential border is connected with the cornea, ciliary muscle, and 
ciliary processes; the free inner edge forms the boundary of the pupil, the 
size of which is constantly changing. The framework of the iris is com¬ 
posed of connective tissue blood-vessels, muscular fibers, and pigmented 
connective-tissue corpuscles. The anterior surface is covered with a layer 
of epithelial cells continuous with those covering the posterior surface of 
the cornea ; the posterior surface is lined by a limiting membrane bearing 
pigment epithelial cells continuous with those of the choroid. The various 
colors which the iris assumes in different individuals depend upon the 
quantity and disposition of the pigmentary granules. 

The muscular fibers of the iris, which are of the non-striated variety, are 
arranged in two sets,— the sphincter and dilator. 

The sphincterpupillce is a circular flat band of muscular fibers surround¬ 
ing the pupil close to its posterior surface; by its contraction and relaxa¬ 
tion, the pupil is diminished or increased in size. The dilator pupillce 
consists of a thin layer of fibers arranged in a radiate manner; at the mar¬ 
gin of the pupil they blend with those of the sphincter muscle, while at the 
outer border they arch to form a circular muscular layer. 

The ciliary muscle is a gray circular band consisting of unstriped muscu¬ 
lar fibers about one-tenth of an inch long running from before backward. 


194 


HUMAN PHYSIOLOGY. 


It is attached anteriorly to the inner surface of the sclerotic and cornea, 
and posteriorly to the choroid coat opposite the ciliary processes. At the 
anterior border of the radiating fibers and internally are found bundles of 
circular muscular fibers, constituting the annular muscle of Muller. The 
ciliary muscle thus consists of two sets of fibers, a radiating and circular, 
both of which are concerned in effecting a change in the convexity of the 
lens in the accommodation of the eye to near vision. 

The Retina forms the internal coat of the eye. In the fresh state it is a 
delicate, transparent membrane of a pink color, but after death soon becomes 


Fig. 24. 



SCLEROTIC COAT REMOVED TO SHOW THE CHOROID, CILIARY MUSCLE, AND NERVES. 

a. Sclerotic coat. b. Veins of the choroid, c. Ciliary nerves, d. Veins of the choroid. 
e. Ciliary muscle, f. Iris .—From Holden’s Anatomy. 

opaque; it extends forward almost to the ciliary processes, where it termi¬ 
nates in an indented border, the ora serrata. In the posterior part of the 
retina at a point corresponding to the axis of vision is a yellow spot, the 
macula lutea , which is somewhat oval in shape and tinged with yellow 
pigment. It presents in its center a depression, the fovea centralis , corres¬ 
ponding to a decrease in thickness of the retina; about one-tenth of an 
inch to the inner side of the macula is the point of entrance of the optic 
nerve. The arteria centralis retince pierces the optic nerve near the 
sclerotic, runs forward in its substance, and is distributed in the retina as far 
forward as the ciliary processes. 










THE SENSE’ OF SIGHT. 


195 


The retina is remarkably complex, consisting of ten distinct layers, from 
within outward, supported by connective tissue. These are as follows, 
viz.; i. Membrana limitans interna. 2. Fibers of optic nerve. 3. 
Layers of ganglionic corpuscles. 4. Molecular layer. 5. Internal granu¬ 
lar layer. 6. Molecular layer. 7. External granular layer. 8. Mem¬ 
brana limitans externa. 9. Jacobson’s membrane, or layer of rods and cones. 
10. The layer of pigment cells. 

The most important of these, however, is the layer of rods and cones in 
the external portion of the retina. The rods are straight, elongated cylinders 
extending through the entire thickness of Jacobson’s membrane. They 
consist of an external portion, which is clear, homogeneous, and highly re¬ 
fracting, and of an internal portion which is slightly granular and less 
refractive; the outer end of each rod is in direct contact with the pig¬ 
mentary epithelium lining the choroid, while the inner end, tapering to a fine 
thread, pierces the external limiting membrane and passes into the external 
granular layer. The cones consist also of two portions, the inner of which 
is somewhat thicker than the rod and rests upon the limiting membrane; 
the outer portion tapers to a fine point, which is known as the cone-style. 
The cones, as a rule, are somewhat shorter than the rods. The propor¬ 
tion of rods to cones varies in different parts of the retina, though there are 
on the average about fourteen rods to one cone. In the macula lutea, where 
vision is most acute, the rods are almost entirely absent, cones alone being 
present. All the retinal elements at this point are changed. The nerve 
fiber layer is absent, the axis cylinders radiating in such a manner as to 
leave the spot free from their covering. The remaining layers are all 
thinned and the stroma reduced to a minimum. The optic nerve after 
passing forward from the brain penetrates in succession the sclerotic, 
choroid, and retina; the nerve fibers then spread out over the anterior 
surface of the retina and become connected with the large ganglionic cells, 
the third layer of the retina. 

The number of optic nerve fibers in the retina is estimated to be about 
800,000, and for each fiber there are about seven cones, one hundred rods, 
and seven pigment cells. The points of the rods and cones are directed 
toward the choroid, or away from the entering light, and dip into the pig¬ 
mentary layer. They, with the pigment layer, are the elements interme¬ 
diating the change of the ethereal vibrations into nerve force; out of these 
nerve vibrations the brain fashions the sensations of light, form, and color. 

The vitreous humor, which supports the retina, is the largest of the re¬ 
fracting media; it is globular in form and constitutes about four-fifths of the 
ball; it is hollowed out anteriorly for the reception of the crystalline lens, 


196 


HUMAN PHYSIOLOGY. 


The outer surface of the vitreous is covered by a delicate, transparent mem¬ 
brane, termed the hyaloid membrane , which serves to maintain its globular 
form. 

The aqueous humor found in the anterior chamber of the eye is a clear 
alkaline fluid, having a specific gravity of 1.003-1.009. It is secreted most 
probably by the blood-vessels of the iris and ciliary processes.' It passes 
from the interior of the eye, through the canal of Schlemm and the meshes 
at the base of the iris, into the anterior circular vein. 

The crystalline lens , enclosed within its capsule, is a transparent bi-con- 
vex body, situated just behind the iris and resting in the depression in the 
anterior part of the vitreous. The two convexities are not quite alike, the 
curvature of the posterior surface being slightly greater than that of the an¬ 
terior. The lens measures about one-third of an inch in the transverse 
diameter and one-fifth of an inch in the antero-posterior diameter. 

The suspensory ligament , by which the lens is held in position, is a firm, 
transparent membrane, united to the ciliary processes. A short distance 
beyond its origin, it splits into two layers, the anterior of which is inserted 
into the capsule of the lens and blends with it; the posterior, passing inward 
behind the lens, becomes united to its capsule. The anterior layer pre¬ 
sents a series of foldings, Zone of Zinn , which are inserted into the inter¬ 
vals of the folds of the ciliary processes. The triangular space between 
the two layers is the canal of Petit. 

Blood-vessels and Nerves.—The structures composing the eyeball are 
supplied with blood by the long and short ciliary arteries, branches of the 
ophthalmic; they pierce the sclerotic at various points and are ultimately 
distributed to all tissues within the ball. 

The nerve supply cSmes largely from the ophthalmic or ciliary ganglion. 
This is a small body, situated in the posterior part of the orbit; it receives 
motor fibers from a branch of the motor-oculi, or third nerve; a sensory 
branch from the ophthalmic division of the fifth nerve and fibers from the 
cavernous plexus of the sympathetic. From the anterior border of the 
ganglion proceed the ciliary nerves, which, entering the eyeball, endow its 
structures with motion and sensation. 

The Eyeball a Living Camera Obscura.—The eyeball may be com¬ 
pared in a general way to a camera obscura. The anatomical arrangement 
of its structures reveal many points of similarity. The sclerotic and choroid 
may be compared with the walls of the chamber; the jcombined refractive 
media, cornea, aqueous humor, lens, and vitreous humor, to the lens for 
focusing the rays of light;.the retina to the sensittve plate receiving the 


THE SENSE OF SIGHT. 


197 


image formed at the focal point; the iris to the diaphragm, which by cutting 
off the marginal rays prevents spherical aberration and at the same time 
regulates the amount of light entering the eye; the ciliary muscle to the 
adjusting screw by which distinct images are thrown upon the retina in 
spite of varying distances of the object from which the light rays emanate. 
The structures just enumerated are those essential for normal vision. 

The relationship of the various structures composing the eyeball is shown 
by the following figure :— 


Fig. 25 



DIAGRAM OF A VERTICAL SECTION OF THE EYE. 
i. Anterior chamber filled with aqueous humor. 3. Posterior chamber. 3. Canal of 

Petit. 

a. Hyaloid membrane, b. Retina (dotted line)., c. Choroid coat (black line), d. 
Sclerotic coat. e. Cornea, f. Iris. g. Ciliary processes, h. Canal of Schlemm 
or Fontana, i. Ciliary muscle .—From Holden’s Anatomy. 

The Dioptric or Refracting apparatus, by which the rays of light enter¬ 
ing the eye are so manipulated as to produce an image on the retina, 
consists of the cornea, aqueous humor, crystalline lens, and vitreous humor. 
A ray of light in passing through each of these media will undergo refrac¬ 
tion at their surfaces and ultimately be brought to a focus at the retina. 
Inasmuch as the two surfaces of the cornea are parallel and its refractive 
power practically the same as the aqueous humor, the media may be re¬ 
duced to three, Viz.: 1. Cornet and aqueous humor. 2. The lens. 3. 
The vitreous humor. The refract ng surfaces may also be reduced to three. 












198 


HUMAN PHYSIOLOGY. 


viz.: I. Anterior surface of the cornea. 2. Anterior surface of lens. 3* 
Posterior surface of lens. 

The refraction effected by the cornea is very great, owing to the passage 
of the light from the air into a comparatively dense medium, and is sufficient 
of itself to bring parallel rays of light to a focus about 10 millimeters behind 
the retina. This would be the condition in an eye in which the lens was 
congenitally absent. Perfect vision requires, however, that the convergence 
of the light shall be great enough that the image may fall upon the retina. 
This is accomplished by the crystalline lens, a body denser than the cornea 
and possessing a higher refractive power. The manner in which a bicon¬ 
vex lens focuses both parallel and divergent rays is shown in the following 
figures:— 

Fig. 26. 



DIAGRAM SHOWING THE COURSE OF PARALLEL RAYS OF LIGHT FROM A, IN THEIR PAS¬ 
SAGE THROUGH A BICONVEX LENS, L, IN WHICH THEY ARE SO REFRACTED AS TO 

bend toward and come in a focus at a point, F. — From Yeo’s Text-Book 0/ 
Physiology. 


Fig. 27. 



DIAGRAM SHOWING THE COURSE OF DIVERGING RAYS WHICH ARE BENT TO A POINT 

FURTHER FROM THE LENS THAN THE PARALLEL RAYS IN PRECEDING FIGURE.— 

From Yeo’s Text-Book of Physiology. 

The function of the crystalline lens, therefore, is to focus the rays of light 
with the formation of an image on the retina. 

The Retinal Image corresponds in all respects to the object from which 
the light proceeds. The existence of this image can be demonstrated by 
removing from the eye of a recently killed animal a circular portion of the 
sclerotic and choroid posteriorly and then placing at the proper distance in 
front of the cornea a lighted candle; an inverted image of the candle will 













THE SENSE OF SIGHT. 


199 


be seen upon the retina. The size of the retinal image depends upon the 
visual angle, which in turn depends upon the size of the object and its 
distance from the eye. At a distance of 15.2596 meters the image of an 
object 1 meter high would be 1 millimeter, or a thousand times smaller 
than the object. 

Accommodation.—By accommodation is understood the power which 
the eye possesses of adjusting itself to vision at different distances. In a 
normal or emmetropic eye parallel rays of light are brought to a focus on 
the retina; but divergent rays, that is, rays coming from a near luminous 
point, will be brought to a focus behind the retina, provided the refractive 
media remain the same; as a result vision would be indistinct, from the 
formation of diffusion circles. It is impossible to see distinctly, therefore, 
a near and distant object at the same time. We must alternately direct 
the vision from one to the other. A normal eye does not require adjust¬ 
ing for parallel rays; but for divergent rays a change in the eye is necessi¬ 
tated; this is termed accommodation. In the accommodation for near 
vision the lens becomes more convex, particularly on its anterior surface; 
the increase in convexity increases its refractive power; the greater the 
degree of divergence of the rays previous to entering the eye, the greater 
the increase of convexity of the lens and convergence of the rays after 
passing through it. By this alteration in the shape of the lens we are 
enabled to focus light rays coming from, and to see distinctly, near as well 
as distant objects. 

Function of the Ciliary Muscle.—Though it is admitted that the 
change in the convexity of the lens is caused by the contraction of the 
ciliary muscle and the relaxation of the suspensory ligament, the exact 
manner in which it does so is not understood. When the eye is in repose, 
as in distant vision, the suspensory ligament is tense and the lens possesses 
that degree of curvature necessary for focusing parallel rays. In the volun¬ 
tary efforts to accommodate the eye for near vision, the ciliary muscle con¬ 
tracts, the suspensory ligament relaxes, and the lens, inherently elastic, 
bulges forward and once again focuses the rays upon the retina. It is, 
therefore, termed the muscle of accommodation, and by its alternate con¬ 
traction and relaxation the lens is rendered more or less convex, accord¬ 
ing to the requirements for near and distant vision. 

Range of Accommodation.—Parallel rays coming from a luminous 
point, distant not less than 200 feet, do not require adjustment; from this 
point up to infinity no accommodation is required for perfect vision. This is 
termed the punctum remotum , and indicates the distance to which an object 


200 


HUMAN PHYSIOLOGY. 


may be removed and yet distinctly seen. If the object be brought nearer 
to the eye than 200 feet, the accommodative power must come into play; 
the nearer the object the more energetic must by the contraction of the 
ciliary muscle and the consequent increase in the convexity of the lens. At 
a distance of five inches, however, the power of accommodation reaches 
its maximum; this is termed the punclum proximum , and indicates the 
nearest point at which an object may be seen distinctly. The distance 
between these two points is the range of accommodation. 

Optical Defects. — Astigmatism is a condition of the eye which pre¬ 
vents vertical and horizontal lines from being focused at the same time, 
and is due to a greater curvature of the cornea in one meridian than 
another. 

Spherical aberration is a condition in which there is an indistinctness of 
an image from the unequal refraction of the rays of light passing through 
the circumference and the center of the lens ; it is corrected mainly by the 
iris, which cuts off the marginal rays, and only transmits those passing 
through the center. 

Chromatic aberration is a condition in which the image is surrounded by 
a colored margin, from the decomposition of the rays of light into their 
elementary parts. 

Myopia , or short-sightedness , is caused by an abnormal increase in the 
antero-posterior diameter of the eyeball, or by a subnormal refracting power 
of the lens; it is generally due to the first cause; the lens being too far 
removed from the retina, forms the image in front of it, and the perception 
becomes dim and blurred. Concave glasses correct this defect by prevent¬ 
ing the rays from converging too soon. 

Hypermetropia , or long-sightedness , is caused by a shortening of the 
antero-posterior diameter, or by an excessive refractive power of the lens; 
the focus of the rays of light would, therefore, be behind the retina. Con¬ 
vex glasses correct this defect by converging the rays of light more an¬ 
teriorly. 

Presbyopia is a loss of the power of accommodation of the eye to near 
objects, and usually occurs between the ages of 40 and 60; it is remedied 
by the use of convex glasses. 

The Iris.—The iris plays the part of a diaphragm, and by means of its 
central aperture the pupil regulates the quantity of light entering the 
interior of the eye; by preventing rays from passing through the margin of 
the lens it diminishes spherical aberration. The size of the pupil depends 
upon the relative degree of contraction of the circular and radiating fibers; 


THE SENSE OF SIGHT. 


201 


the variations in size of the pupil from variations in the degree of contrac¬ 
tion depend upon different intensities of light. If the light be intense, the 
circular fibers contract and diminish the size of the pupil; if the light 
diminishes in intensity, the circular fibers relax and the pupil enlarges. 

Point of Most Distinct Vision.—While all portions of the retina are 
sensitive to light, their sensibility varies within wide limits. At the macula 
lutea, and more especially in its most central depression, the fovea, where 
the retinal elements are reduced practically to the layer of rods and cones, 
the sensibility reaches its maximum. It is at this point that the image is 
found when vision is most distinct. The macula and fovea are always in 
the line of direct vision. From the macula toward the periphery of the 
retina there is a gradual diminution in sensibility and a corresponding 
decline in the distinctness of vision. In those portions of the retina lying 
outside the macula the indistinctness of vision depends not only on dimin¬ 
ished sensibility, but also upon inaccurate focusing of the rays. 

Blind Spot.—Although the optic nerve transmits the impulses excited 
in the retina by the ethereal vibration, the nerve fibers themselves are insen¬ 
sitive to light. At the point of entrance of the optic nerve, owing to the 
absence of the rods and cones, the rays of light make no impression. This 
is the blind spot. As this spot is not in the line of vision, no dark point is 
ordinarily observed in the field of vision, that circular space before a fixed 
eye within which objects are perceptible. 

The rods and cones are the most sensitive portions of the retina. A ray 
of light entering the eye passes entirely through the various layers of the 
retina and is arrested only upon reaching the pigmentary epithelium in 
which the rods and cones are imbedded. As to the manner in which the 
objective stimuli, light, and color so-called, are transformed into nerve im¬ 
pulses, but little is known. It is probable that the ethereal vibrations are 
transformed into heat, which excites the rods and cones. These, acting as 
highly specialized end organs of the optic nerve, start the impulses on their 
way to the brain, where the seeing process takes place. As to the relative 
function of the rods and cones, it has been suggested, from the study of the 
facts of comparative anatomy, that the rods are impressed only by differences 
in the intensity of light, while the cones in addition are impressed by quali¬ 
tative differences or color. 

Accessory Structures.—The muscles which move the eyeball are six 
in number: the superior and inferior recti, the external and internal recti, 
the superior and inferior oblique muscles. The four recti muscles, arising 
from the apex of the orbit, pass forward and are inserted into the sides of 
N 


202 


HUMAN PHYSIOLOGY. 


the sclerotic coat; the superior and inferior muscles rotate the eye around 
a horizontal axis; the external and internal rotate it around a vertical 
axis. 

The superior oblique muscle, having the same origin, passes forward to 
the inner and upper angle of the orbital cavity, where its tendon passes 
through a cartilaginous pully; it is then reflected backward and inserted 
into the sclerotic just behind the transverse diameter. Its function is to 
rotate the eyeball in such a manner as to direct the pupil downward and 
outward. 

The inferior oblique muscle arises at the inner angle of the orbit and 
then passes outward and backward, to be inserted into the sclerotic. Its 
function is to rotate the eyeball and direct the pupil upward and outward. 

By the associated action of all these muscles, the eyeball is capable of 
performing all the varied and complex movements necessary for distinct 
vision. 

The eyelids , bordered with short, stiff hairs, shade the eye and protect it 
from injury. On the posterior surface, just beneath the conjunctiva, are 
the Meibomian glands, which secrete an oily fluid; it covers the edge of 
the lids, and prevents the tears from flowing over the cheek. 

The lachrymal glands are ovoid in shape, and situated at the upper and 
outer part of the orbital cavity ; they open by from six to eight ducts at the 
outer portion of the upper lids. 

The tears , secreted by the lachrymal glands, are distributed over the 
cornea by the lids during the act of winking, and keep it moist and free 
from dust. The excess of tears passes.into the lachrymal ducts, which 
begin by two minute orifices, one on each lid, at the inner canthus. They 
conduct the tears into the nasal duct, and so into the nose. 


THE SENSE OF HEARING. 

The Ear, or Organ of Hearing, is lodged within the petrous portion 
of the temporal bone. It may be, for convenience of description, divided 
into three portions, viz.: i. The external ear. 2. The middle ear. 3. The 
internal ear or labyrinth. 

The External Ear consists of the pinna or auricle and the external au¬ 
ditory canal. The pinna consists of a thin layer of cartilage, presenting a 
series of elevations and depressions; it is attached by fibrous tissue to the 
outer bony edge of the auditory canal; it is covered by a layer of integu¬ 
ment continuous with that covering the side of the head. The general 


THE SENSE OF HEARING. 


203 


shape of the pinna is concave and presents a little below the center a deep 
depression, the concha. The external auditory canal extends from the 
concha inward for a distance of about one and a quarter inches. It is 
directed somewhat forward and upward, passing over a convexity of bone, 
and then dips downward to its termination; it is composed of both bone 
and cartilage and lined by a reflection of the skin covering the pinna. At 
the external portion of the canal the skin contains a number of tubular 
glands, the ceruminous glands , which in their conformation resemble the 
perspiratory glands. They secrete the cerumen or ear wax. 

The Middle Ear, or Tympanum, is an irregularly shaped cavity hol¬ 
lowed out of the temporal bone and situated between the external ear and 
the labyrinth. It is narrow from side to side but relatively long in its 
vertical and antero-posterior diameters; it is separated from the external 
auditory canal by a membrane, the mejnbrana tympani; from the internal 
ear it is separated by an osseo-membranous partition which forms a common 
wall for both cavities. The middle ear communicates posteriorly with the 
mastoid cells, anteriorly with the naso-pharynx by means of the Eustachian 
tube. The interior of this cavity is lined by mucous membrane continuous 
with that lining the pharynx. 

The membrana tympani is a thin, translucent, nearly circular membrane, 
measuring about two-fifths of an inch in diameter, placed at the inner ter¬ 
mination of the external auditory canal. The membrane is inclosed within 
a ring of bone which, in the fetal condition, can be easily removed, but in 
the adult condition becomes consolidated with the surrounding bone. The 
membrana tympani consists primarily of a layer of fibrous tissue, arranged 
both circularly and radially, and forms the membrana propria; externally 
it is covered by a thin layer of skin continuous with that lining the auditory 
canal; internally, it is covered by a thin mucous membrane. The tympanic 
membrane is placed obliquely at the bottom of the auditory canal, inclining 
at an angle of 45 0 , being directed from behind and above downward and 
inward. On its external surface this membrane presents a funnel-shaped 
depression, the sides of which are somewhat convex. 

The Ear-bones. Running across the tympanic cavity and forming an 
irregular line of jointed levers, is a chain of bones which articulate with 
each other at their extremities. They are known as the malleus, incus, and 
stapes. 

The form and position of these bones are shown in Fig. 28. 

The malleus consists of a head, neck, and handle, of which the latter is 
attached to the inner surface of the membrana tympani; the incus , or anvil 


204 


HUMAN PHYSIOLOGY. 


bone, presents a concave, articular surface, which receives the head of the 
malleus; the stapes, or stirrup bone, articulates externally with the long pro¬ 
cess of the incus, and internally, by its oval base, with the edges of the fora¬ 
men ovale. 

The Tensor Tympani Muscle consists of a fleshy, tapering portion, half 
an inch in length, which terminates in a slender tendon; it arises from the 


Fig. 28. 



TYMPANUM AND AUDITORY OSSICLES (LEFT) MAGNIFIED. 

A.G., external meatus ; M, membrana tympani, which is attached to the handle of the 
malleus, n, and near it the short process, h, head of the malleus; a, incus ; k, its 
short process with its ligament: /, long process; s, Sylvian ossicle; S, stapes ; Ax, 
Ax, is the axis of rotation of the ossicles; it is shown in perspective, and must be 
imagined to penetrate the plane of the paper; /, line of traction of the tensor tympani. 
The other arrows indicate the movement of the ossicles when the tensor contracts. 


cartilaginous portion of the Eustachian tube and adjacent surface of the 
sphenoid bone. From this origin the muscle passes nearly horizontally 
backward to the tympanic cavity; just opposite to the fenestra ovalis its 
tendon bends at a right angle over the processus cochleariformis and then 
passes outward across the cavity to be inserted into the handle of the mal¬ 
leus near the neck. 


THE SENSE OF HEARING. 


205 


The Stapedius Muscle emerges from the cavity of a pyramid of bone 
projecting from the posterior wall of the tympanum; the tendon passes 
forward and is inserted into the neck of the stapes bone posteriorly near its 
point of articulation with the incus. 

The laxator tympani muscle, so-called, is now generally regarded as liga¬ 
mentous in nature, and not muscular. 

The Eustachian Tube, by means of which a free communication is 
established between the middle ear and pharynx, is partly bony and partly 
cartilaginous in structure. It measures about an inch and a half in length ; 
commencing at its opening into the naso-pharynx it passes upward and out¬ 
ward to the spine of the sphenoid bone, at which point it becomes some¬ 
what contracted; the tube then dilates as it passes backward into the middle 
ear cavity; it is lined by mucous membrane, which is continued into the 
middle ear and mastoid cells. 

The Function of the Ear, as a whole, is the reception and transmis¬ 
sion of aerial vibrations to the terminal organs concealed within the in¬ 
ternal ear and which are connected with the auditory nerve fibers. The 
excitation of these end organs caused by the impact of the vibrations 
arouses in the auditory nerve impulses which are then transmitted to the 
brain, where the hearing process takes place. In order to appreciate the 
functions of the individual parts of the ear a few of the characteristics of 
sound waves must be kept in mind. 

Sound Waves.—All sounds are caused by vibrations in the atmosphere 
which have been communicated to it by vibrating elastic bodies, such as 
membranes, strings, rods, etc. These vibrating bodies produce in the air 
a to-and-fro movement of its particles, resulting in a series of alternate 
condensations and rarefactions, which are propagated in all directions. A 
complete oscillation of a particle of air forward and backward constitutes a 
sound-wave. Musical sounds are caused by a succession of regular waves, 
which follow each other with a certain rapidity. Noises are caused by the 
impact of a series of irregular waves. 

All sound waves possess intensity, pitch, and quality. The intensity, or 
loudness, of a sound depends upon the amplitude of the vibration or the 
extent of its excursion. The pitch depends upon the number of vibrations 
which affect the auditory nerve in a second of time; the pitch of the note 
C, the first below the leger line of the musical scale, is caused by 256 
vibrations per second; the pitch of the same note an octave higher is 
caused by 512 vibrations per second. If the vibrations are too few per 
second they fail to be perceived as a continuous sound; the minimum 


206 


HUMAN PHYSIOLOGY. 


number of vibrations capable of producing a sound has been fixed at 16 per 
second; the highest pitched musical note capable of being heard has been 
shown to be due to 38,000 vibrations per second. In the ascent of the 
musical scale there is, therefore, a gradual increase in the number of vibra¬ 
tions and a gradual increase in the pitch of the sounds. Between the two 
extreme limits lies the range of audibility, which embraces eleven octaves, 
of which seven are employed in the musical scale. 

The quality of sound depends upon a combination of the fundamental 
vibration with certain secondary vibrations of subdivisions of the vibrating 
body. These so-called over-tones vary in intensity and pitch, and by 
modifying the form of the primary wave produce that which is termed the 
quality of sound. 

Function of the Pinna and External Auditory Canal.—In those 
animals possessing movable ears, the pinna plays an important part in the 
collection of sound-waves. In man, in whom the capability of moving the 
pinna has been lost, it is doubtful if it is at all necessary for hearing. Never¬ 
theless, an individual with dull hearing may have the perception of sound 
increased by placing the pinna at an angle of 45 0 to the side of the head. 
The external auditory canal transmits the sonorous vibrations to the tym¬ 
panic membrane. Owing to the obliquity of this canal it has been sup¬ 
posed that the waves, concentrated at the concha, undergo a series of re¬ 
flections on their way to the tympanic membrane, and, owing to the posi¬ 
tion of this membrane, strike it almost perpendicularly. 

Function of the Tympanic Membrane.—The function of the tym- 
panic membrane appears to be the reception of sound vibrations by being 
thrown by them into reciprocal vibrations which correspond in intensity and 
amplitude. That this membrane actually reproduces all vibrations within 
the range of audibility has been experimentally demonstrated. The mem¬ 
brane not being fixed, as far as its tension is concerned, does not possess a 
fixed fundamental note, like a stationary fixed membrane, and is therefore 
just as well adapted for the reception of one set of vibrations as another. 
This is made possible by variations in its tension in accordance with the 
pitch of the sounds. In the absence of all sound the membrane is in a 
condition of relaxation; with the advent of sound-waves possessing a 
gradual increase of pitch, as in the ascent of the musical scale, the tension 
of the tympanic membrane is gradually increased until its maximum ten¬ 
sion is reached at the upper limit of the range of audibility. By this change 
in tension certain tones become perceptible and distinct, while others be¬ 
come indistinct and inaudible. 



THE SENSE OF HEARING. 


207 


Function of the Tensor Tympani Muscle.—The function of this 
muscle is, as its name indicates, to increase the tension of the membrane in 
accordance with the pitch of the sound wave. The tendon of this muscle 
playing over the processus cochleariformis and attached at almost a right 
angle to the handle of the malleus will, when the muscle contracts, pull 
the handle inward, increase the convexity of the membrane, and at the 
same time increase its tension; with the relaxation of this muscle, the handle 
of the malleus passes outward and the tension is diminished. The con¬ 
tractions of the tensor muscle are reflex in character and excited by nerve 
impulses reaching it through the small petrosal nerve and otic ganglion. 
The number of nerve stimuli passing to the muscle and determining the 
degree of contraction will depend upon the pitch of the sound wave and 
the subsequent excitation of the auditory nerve. The tensor tympani mus¬ 
cle may be regarded as an accommodative apparatus by which the tym¬ 
panic membrane is adjusted to enable it to receive vibrations of varying 
degrees of pitch. 

Function of the Ossicles.—The function of the chain of bones is to 
transmit the sound waves across the tympanic cavity to the internal ear. 
The first of these bones, the malleus, being attached to the tympanic mem¬ 
brane, will take up the vibrations much more readily than if no membrane 
intervened. Owing to the character of the articulations, when the handle 
of the malleus is drawn inward, the position of the bones is so changed 
that they form practically a solid rod, and are therefore much better adapted 
for the transmission of molecular vibrations than if the articulations re¬ 
mained loose. As the stapes bone is somewhat shorter than the malleus, 
its vibrations are smaller than those of the tympanic membrane, and by 
this arrangement the amplitude of the vibrations is diminished, but their 
force increased. 

The Function of the Stapedius Muscle is, according to Henle, to 
fix the stapes bone so as to prevent too great a movement from being com¬ 
municated to it from the incus and transmitted to the perilymph. It may 
be looked upon, therefore, as a protective muscle. 

The Function of the Eustachian Tube is to maintain a free com¬ 
munication between the cavity of the middle ear and naso-pharynx. The 
pressure of air within and without the ear is thus equalized, and the vibra¬ 
tions of the tympanic membrane permitted to attain their maximum, one 
of the conditions essential for the reception of sound waves. The impair¬ 
ment in the acuteness of hearing which is caused by an unequal pressure of 
the air in the middle ear can be shown : I. By closing the mouth and nose 


208 


HUMAN PHYSIOLOGY. 


and forcing air from the lungs through the Eustachian tube into the ear, 
producing an increase in pressure. 2. By closing the nose and mouth, and 
making efforts at deglutition, which withdraws the air from the ear and 
diminishes its pressure. In both instances the free vibrations of the tym¬ 
panic membrane are interfered with. The pharyngeal orifice of the Eus¬ 
tachian tube is opened by the action of certain of the muscles of deglutition, 
viz.: the levator palati, tensor palati, and the palato-pharyngei muscles. 

The Internal Ear, or Labyrinth, is located in the petrous portion of 
the temporal bone, and consists of an osseous and membranous portion. 

The Osseous Labyrinth is divisible into three parts, viz.: the vesti¬ 
bule, the semicircular canals, and the cochlea. • 

The vestibule is a small triangular cavity, which communicates with the 
middle ear by the foramen ovale; in the natural condition it is closed by 
the base of the stapes bone. The filaments of the auditory nerve enter the 
vestibule through small foramina in the inner wall, at the fovea hemi- 
spherica. 

The semicircular canals are three in number, the superior vertical, the 
inferior vertical, and the horizontal, each of which opens into the cavity of 
the vestibule by two openings, with the exception of the two vertical, which 
at one extremity open by a common orifice. 

The cochlea forms the anterior part of the internal ear. It is a gradually 
tapering canal, about one and a half inches in length, which winds spirally 
around a central axis, the modiolus , two and a half times. The interior of 
the cochlea is partly divided into two passages by a thin plate of bone, the 
lamina osseous spiralis , which projects from the central axis two thirds 
across the canal. These passages are termed the scala vestibuli and the 
scala iympani, from their communication with the vestibule and tympanum. 
The scala tympani communicates with the middle ear through the foramen 
rotundum , which, in the natural condition, is closed by the second mem- 
brana tympani ; superiorly they are united by an opening, the helicotrema. 

The whole anterior of the labyrinth, the vestibule, the semicircular 
canals, and the scala of the cochlea, contains a clear, limpid fluid, the peri¬ 
lymph, secreted by the periosteum lining the osseous walls. 

The Membranous Labyrinth corresponds to the osseous labyrinth 
with respect to form, though somewhat smaller in size. 

The vestibular portion consists of two small sacs, the utricle and saccule. 

The semicircular canals communicate with the utricle in the same 
manner as the bony canals communicate with the vestibule. The saccule 
communicates with the membranous cochlea by the canalis reuniens. In 


THE SENSE OF HEARING. 


209 


the interior of the utricle and saccule, at the entrance of the auditory nerve, 
are small masses of carbonate of lime crystals, constituting the otoliths. 
Their function is unknown. 

The membranous cochlea is a closed tube, commencing by a blind 
extremity at the first turn of the cochlea, and terminating at its apex by a 
blind extremity also. It is situated between the edge of the osseous lamina 
spiralis and the outer wall of the bony cochlea, and follows it in its turns 
around the modiolus. 

A transverse section of the cochlea shows that it is divided into two 
portions by the osseous lamina and the basilar membrane: I. The scala 
vestibuli, bounded by the periosteum and membrane of Reissner. 2. The 
scala tympani , occupying the inferior portion, and bounded above by the 
septum, composed of the osseous lamina and the membrana basilaris. 

The true membranous canal is situated between the membrane of Reiss¬ 
ner and the basilar membrane. It is triangular in shape, but is partly 
divided into a triangular portion and a quadrilateral portion by th o. tectorial 
membrane. 

The organ of Corti is situated in the quadrilateral portion of the canal, 
and consists of pillars of rods, of the consistence of cartilage. They are 
arranged in two rows—the one internal, the other external; these rods rest 
upon the basilar membrane; their bases are separated from each other, but 
their upper extremities are united, forming an arcade. In the internal row 
it is estimated there are about 3500, and in the external row about 5200 of 
these rods. 

On the inner side of the internal row is a single layer of elongated hair 
cells; on the outer surface of the external row are three such layers of hair 
cells. Nothing definite is known as to their function. 

The endolymph occupies the interior of the utricle, saccule, membranous 
canals, and bathes the strictures iq the interior of the membranous cochlea 
throughout its entire extent. 

The Auditory Nerve at the bottom of the internal auditory meatus 
divides into (1) a vestibular branch, which is distributed to the utricle and 
semicircular canals; (2) a cochlear branch, which passes into the central 
axis at its base, and ascends to its apex; as it ascends, fibers are given off, 
which pass between the plates of the osseous lamina, to be ultimately con¬ 
nected with the organ of Corti. 

The function of the semicircular canals appears to be to assist in main¬ 
taining the equilibrium of the body; destruction of the vertical canal is 
followed by an oscillation of the head upward and downward ; destruction 
of the horizontal canal is followed by oscillations from left to right. When 


210 


HUMAN PHYSIOLOGY. 


the canals are injured on both sides, the animal loses the power of main¬ 
taining equilibrium upon making muscular movements. 

Function of the cochlea. It is regarded as possessing the power of 
appreciating the quality of pitch and the shades of different musical tones. 
The elements of the organ of Corti are analogous, in some respects, to a 
musical instrument, and are supposed, by Helmholtz, to be tuned so as to 
vibrate in unison with the different tones conveyed to the internal ear. 

Summary.—The waves of sound are gathered together by the pinna 
and external auditory meatus, and conveyed to the membrana tympani. 
This membrane, made tense or lax by the action of the tensor tympani 
and laxator tympani muscles, is enabled to receive sound waves of either 
a high or low pitch. The vibrations are conducted across the middle ear 
by a chain of bones to the foramen ovale, and by the column of air of 
the tympanum to the foramen rotundum, which is closed by the second 
membrana tympani, the pressure of the air in the tympanum being regu¬ 
lated by the Eustachian tube. 

The internal ear finally receives the vibrations, which excite vibrations 
successively in the perilymph, the walls of the membranous labyrinth, the 
endolymph, and, lastly, the terminal filaments of the auditory nerve, by 
which they are conveyed to the brain. 


VOICE AND SPEECH. 

The Larynx is the organ of voice. Speech is a modification of voice, 
and is produced by the teeth and the muscles of the lips and tongue, co¬ 
ordinated in their action by stimuli derived from the cerebrum. 

The Structures entering into the formation of the larynx are mainly 
the thyroid , cricoid, and arytenoid cartilages; they are so situated and 
united by means of ligaments and muscles as to form a firm cartilaginous - 
box. The larynx is covered externally by fibrous tissue, and lined inter¬ 
nally with mucous membrane. 

The Vocal Cords are four ligamentous bands, running antero-posteri¬ 
orly across the upper portion of the larynx, and are divided into the two 
superior or false vocal cords, and the two inferior or true vocal cords; 
they are attached anteriorly to the receding angle of the thyroid cartilages 
and posteriorly to the anterior part of the base of the arytenoid cartilages. 
The space between the true vocal cords is the rima glottidis. 

The Muscles which have a direct action upon the movements of the 


VOICE AND SPEECH. 


211 


vocal cords are nine in number, and take their names from their points of 
origin and insertion, viz.: the two crico-thyroid , two thyro-arytenoid , two 
posterior crico-arytenoid, two lateral crico-arytenoid, and one arytenoid 
muscles. 

The crico-thyroid muscles, by their contraction, render the vocal cords 
more tense by drawing down the anterior portion of the thyroid cartilage 
and approximating it to the cricoid, and at the same time tilting the pos¬ 
terior portion of the cricoid and arytenoid cartilages backward. 

The thyro-arytenoid, by their contraction, relax the vocal cords by draw¬ 
ing the arytenoid cartilage forward and the thyroid backward. 

The posterior crico-arytenoid muscles, by their contraction, rotate the 
arytenoid cartilages outward and thus separate the vocal cords and enlarge 
the aperture of the glottis. They principally aid the respiratory movements 
during inspiration. 

The lateral crico-arytenoid muscles are antagonistic to the former, and 
by their contraction rotate the arytenoid cartilages so as to approximate the 
vocal cords and constrict the glottis. 

The arytenoid muscle assists in the closure of the aperture of the glottis. 

The inferior laryngeal nerve animates all the muscles of the larynx, with 
the exception of the crico-thyroid. 

Movements of the Vocal Cords.—During respiration the move¬ 
ments of the vocal cords differ from those occurring during the production 
of voice. 

At each inspiration, the true vocal cords are widely separated, and the 
aperture of the glottis is enlarged by the action of the crico-arytenoid 
muscles, which rotate outward the anterior angle of the base of the aryte¬ 
noid cartilages; at each expiration the larynx becomes passive; the 
elasticity of the vocal cords returns them to their original position, and the 
air is forced out by the elasticity of the lungs and the walls of the thorax. 

Phonation .—As soon as phonation is about to be accomplished a marked 
change in the glottis is noticed with the aid of the laryngoscope. The 
true vocal cords suddenly become approximated and are made parallel, 
giving to the glottis the appearance of a narrow slit, the edges of which are 
capable of vibrating accurately and rapidly ; at the same time their tension 
is much increased. 

With the vocal cords thus prepared, the' expiratory muscles force the 
column of air into the lungs and trachea through the glottis, throwing the 
edges of the cords into vibration. 

The pitch of sounds depends upon the extent to which the vocal cords 
are made tense and the length of the aperture through which the air passes. 


212 


HUMAN PHYSIOLOGY. 


In the production of sounds of a high pitch the tension of the vocal cords 
becomes very marked, and the glottis diminished in length. When grave 
sounds having a low pitch are omitted from the larynx, the vocal cords 
are less tense and their vibrations are large and loose. 

The quality of voice depends upon the length, size, and thickness of the 
cords, and the size, form, and construction of the trachea, larynx, and the 
resonant cavities of the pharynx, nose, and mouth. 

The compass of the voice comprehends from two to three octaves. The 
range is different in the two sexes, the lowest note of the male being about 
one octave lower than the lowest note of the female; while the highest note 
of the male is an octave less than the highest note of the female. 

The varieties of voices, e.g., bass, baritone, tenor, contralto, mezzo- 
soprano, and soprano, are due to the length of the vocal cords, being 
longer when the voice has a low pitch, and shorter when it has a fcigh pitch. 

Speech is the faculty of expressing ideas by means of combinations of 
sounds, in obedience to the dictates of the cerebrum. 

Articulate sounds may. be divided into vowels and consonants. The 
vowel sounds , a , e, i, o, u , are produced in the larynx by the vocal cords. 
The consonantal sounds are produced in the air passages above the larynx 
by an interruption of the current of air by the lips, tongue, and teeth ; the 
consonants may be divided into: (i) mutes, b , d , k^p^i, c,g; (2) dentals, 
s,t,z; (3) nasals, m, n, ng ; (4) labials, 3 ,/,/, v, in; (5) gutturals, 
k, g , c , and g hard; (6) liquids, /, m, n, r. 


GENERATIVE ORGANS OF THE FEMALE. 


213 


REPRODUCTION. 

Reproduction is the function by which the species is preserved, and 
accomplished by the organs of generation in the two sexes. 

GENERATIVE ORGANS OF THE FEMALE. 

The Generative Organs of the Female consist of the ovaries, Fallo¬ 
pian tubes, uterus, and vagina. 

The Ovaries are two small, ovoid, flattened bodies, measuring one inch 
and a half in length and three-quarters of an inch in width ; they are situ¬ 
ated in the cavity of the pelvis, and imbedded in the posterior layer of the 
broad ligament; attached to the uterus by a round ligament, and to the ex¬ 
tremities of the Fallopian tubes by the fimbriae. The ovary consists of an 
external membrane of fibrous tissue, the cortical portion, in which are im¬ 
bedded the Graafian vesicles , and an internal portion, the stroma, contain¬ 
ing blood-vessels. 

The Graafian Vesicles are exceedingly numerous, but situated only in 
the cortical portion. Although the ovary contains the vesicles from the 
period of birth, it is only at the period of puberty that they attain their full 
development. From this time onward to the catamenial period there is a 
constant growth and maturation of the Graafian vesicles. They consist of 
an external investment, composed of fibrous tissue and blood-vessels, in the 
interior of which is a layer of cells forming the membrana granulosa ; at 
its lower portion there is an accumulation of cells, the proligerous disc, in 
which the ovu?n is contained. The cavity of the vesicle contains a slightly 
yellowish, alkaline, albuminous fluid. 

The Ovum is a globular body, measuring about the of an inch in 
diameter; it consists of an external investing membrane,the vitelline mem¬ 
brane ; a central granular substance, the vitellus or yelk; a nucleus, the 
germinal vesicle, in the interior of which is imbedded the nucleolus, or 
germinal spot. 

The Fallopian Tubes are about four inches in length, and extend out¬ 
ward from the upper angles of the uterus, between the folds of the broad 
ligaments, and terminate in a fringed extremity which is attached by one of 
the fringes to the ovary. They consist of three coats : (i) the external, or 


214 


HUMAN PHYSIOLOGY. 


peritoneal, (2) middle, or muscular, the fibers of which are arranged in a 
circular or longitudinal direction, (3) internal, or mucous, covered with 
ciliated epithelial cells, which are always waving from the ovary toward 
the uterus. 

The Uterus is pyriform in shape, and may be divided into a body and 
neck; it measures about three inches in length and two inches in breadth 
in the unimpregnated state. At the lower extremity of the neck is the os 
externum ; at the junction of the neck with the body is a constriction, the 
os internum. The cavity of the uterus is triangular in shape, the walls of 
which are almost in contact. 

The walls of the uterus are made up of several layers of non-striated 
muscular fibers, covered externally by peritoneum, and lined internally by 
mucous membrane, containing numerous tubular glands, and covered by 
ciliated epithelial cells. 

The Vagina is a membranous canal, from five to six inches in length, 
situated between the rectum and bladder. It extends obliquely upward 
from the surface, almost to the brim of the pelvis, and embraces at its upper 
extremity the neck of the uterus. 

Discharge of the Ovum.—As the Graafian vesicle matures, it in¬ 
creases in size, from an augmentation of its liquid contents, and approaches 
the surface of the ovary, where it forms a projection, measuring from one- 
fourth to one-half an inch in size. The maturation of the vesicle occurs 
periodically, about every twenty-eight days, and is attended by the phe¬ 
nomena of menstruation. During this period of active congestion of the 
reproductive organs, the Graafian vesicle ruptures, the ovum and liquid 
contents escape, and are caught by the fimbriated extremity of the Fallo¬ 
pian tube, which has adapted itself to the posterior surface of the ovary. 
The passage of the ovum through the Fallopian tube into the uterus 
occupies from ten to fourteen days, and is accomplished by muscular con¬ 
traction and the action of the ciliated epithelium. 

Menstruation is a periodical discharge of blood from the mucous mem¬ 
brane of the uterus, due to a fatty degeneration of the small blood-vessels. 
Under the pressure of an increased amount of blood in the reproductive 
organs, attending the process of ovulation, the blood-vessels rupture, and a 
hemorrhage takes place into the uterine cavity; thence it passes into the 
vagina. Menstruation lasts from five to six days, and the amount of blood 
discharged averages about five ounces. 

Corpus Luteum.—For some time anterior to the rupture of a Graafian 
vesicle, it increases in size and becomes vascular; its walls become thick- 


GENERATIVE ORGANS OF THE FEMALE. 


215 


ened from the deposition of a reddish-yellow, glutinous substance, a pro¬ 
duct of cell growth from the proper coat of the follicle and the membrana 
granulosa. After the ovum escapes, there is usually a small effusion of 
blood into the cavity of the follicle, which soon coagulates, loses its color¬ 
ing matter, and acquires the characteristics of fibrin, but it takes no part in 
the formation of the corpus luteum. The walls of the follicle become con¬ 
voluted, vascular, and undergo hypertrophy, until they occupy the whole 
of the follicular cavity. At its period of fullest development, the corpus 
luteum measures three fourths of an inch in length and half an inch in 
depth. In a few weeks the mass loses its red color, and becomes yellow, 
constituting the corpus luteum , or yellow body. It then begins to retract 
and becomes pale; and at the end of two months nothing remains but a 
small cicatrix upon the surface of the ovary. Such are the changes in the 
follicle if the ovum has not been impregnated. 

The corpus luteum, after impregnation has taken place, undergoes a 
much slower development, becomes larger, and continues during the entire 
period of gestation. The difference between the corpus luteum of the 
unimpregnated and pregnant condition is expressed in the following table 
by Dalton :— 


Corpus Luteum of Menstruation. Corpus Luteum of Pregnancy. 


At the end of 
three weeks. 
One month. 


Two months. 


Four months. 


Six months. 


Nine months. 


Three-quarters of an inch in diameter; central clot 


reddish ; convoluted wall 
Smaller; convoluted 
wall bright yellow; clot 
still reddish. 

Reduced to the condi¬ 
tion of an insignificant 
cicatrix. 

Absent or unnoticeable. 


Absent. 


Absent. 


pale. 

Larger; convoluted wall 
brfght yellow; clot still red¬ 
dish. 

Seven-eighths of an inch 
in diameter; convoluted wall 
bright yellow; clot perfectly 
decolorized. 

Seven-eighths of an inch 
in diameter; clot pale and 
fibrinous; convoluted wall 
dull yellow. 

Still as large as at the end 
of second month; clot fibrin¬ 
ous ; convoluted wall paler. 

Half an inch in diameter; 
central, clot converted into a 
radiating cicatrix; external 
wall tolerably thick and con¬ 
voluted, ' but without any 
bright yellow color. 




21G 


HUMAN PHYSIOLOGY. 


GENERATIVE ORGANS OF THE MALE. 

The Generative Organs of the Male consist of the testicles, vasa 
deferentia, vesiculae seminales, and penis. 

The Testicles, the essential organs of reproduction in the male, are 
two oblong glands, about an inch and a half in length, compressed from 
side to side, and situated in the cavity of the scrotum. 

The proper coat of the testicle, the tunica albuginea, is a white, fibrous 
structure, about the of an inch in thickness ; after enveloping the testicle, 
it is reflected into its interior at the posterior border, and forms a vertical 
process, the mediastinum testes , from which septa are given off, dividing 
the testicle in lobules. 

The substance of the testicle is made up of the seminiferous tubules , 
which exist to the number of 840; they are exceedingly convoluted, and 
when unraveled are about 30 inches in length. As they pass toward the 
apices of'the lobules they become less convoluted, and terminate in from 
20 to 30 straight ducts, the vasa recta , which pass upward through the 
jnediastinum and constitute the rete testis. At the upper part of the 
mediastinum the tubules unite to form from 9 to 30 small ducts, the vasa 
efferentia , which become convoluted, and form the globus major of the 
epididymis; the continuation of the tubes downward behind the testicle 
and a second convolution constitutes the body and globus minor. 

The seminal tubule consists of a basement membrane lined by granular 
nucleated epithelium. 

The Vas Deferens, the excretory duct of the testicle, is about two feet 
in length, and maybe traced upward from the epididymis to the under sur¬ 
face of the base of the bladder, where it unites with the duct of the vesicula 
seminalis, to form the ejaculatory duct. 

The Vesiculae Seminales r are two lobulated, pyriform bodies, about 
two inches in length, situated on the inner surface of the bladder. 

They have an external fibrous coat, a middle muscular coat, and an 
internal mucous coat, covered by epithelium, which secrets a mucous fluid. 
The vesiculae seminales serve as reservoirs, in which the seminal fluid is 
temporarily stored up. 

The Ejaculatory Duct, about if of an inch in length, opens into the 
urethra, and is formed by the union of the vasa deferentia and the ducts of 
the vesiculae seminales. 

The Prostate Gland surrounds the posterior extremity of the urethra, 
and opens into it by from twenty to thirty openings, the orifices of the pros - 


DEVELOPMENT OF ACCESSORY STRUCTURES. 


217 


tatic tubules. The gland secretes a fluid which forms part of the semen 
and assists in maintaining the vitality of the spermatozoa. 

Semen is a complex fluid, made up of the secretions from the testicles, 
the vesicula seminales, the prostatic and urethral glands. It is grayish- 
white in color, mucilaginous in consistence, of a characteristic odor, and 
somewhat heavier than water. From half a dram to a dram is ejaculated 
at each orgasm. 

The Spermatozoa are peculiar anatomical elements, developed within 
the seminal tubules, and possess the power of spontaneous movement. 
The spermatozoa consist of a conoidal head and a long, filamentous tail, 
which is in continuous and active motion; as long as they remain in the 
vas deferens they are quiescent, but when free to move in the fluid of the 
vesiculae seminales become very active. 

Origin.—The spermatozoa appear at the age of puberty, and are then 
constantly formed until an advanced age. They are developed from the 
nuclei of large, round cells contained in the anterior of the seminal tubules, 
as many as fifteen to twenty developing in a single cell. 

When the spermatozoa are introduced into the vagina, they pass readily 
into the uterus and through the Fallopian tubes toward the ovaries, where 
they remain and retain their vitality for a period of from eight to ten days. 

Fecundation is the union of the spermatozoa with the ovum during its 
passage toward the uterus, and usually takes place in the Fallopian tube, 
just outside of the womb. After floating around the ovum in an active man¬ 
ner, they penetrate the vitelline membrane, pass into the interior of the 
vitellus, where they lose their vitality, and along with the germinal vesicle 
entirely disappear. 


DEVELOPMENT OF ACCESSORY STRUCTURES. 

Segmentation of the Vitellus.—After the disappearance of the 
spermatozoa and the germinal vesicle there remains a transparent, granular, 
albuminous substance, in the center of which a new nucleus soon appears; 
this constitutes the parent cells, and is the first stage in the development of 
the new being. 

Following this, the vitellus undergoes segmentation; a constriction 
appears on the opposite side of the vitellus, which gradually deepens, 
until the yelk is divided into two segments, each of which has a distinct 
nucleus and nucleolus ; these two segments undergo a further division into 
four, the four into eight, the eight into others, and so on, until the entire 


o 


218 


HUMAN PHYSIOLOGY. 


vitellus is divided into a great number of cells, each of which contains a 
nucleus and nucleolus. 

The peripheral cells of this “ mulberry mass ” then arrange themselves 
so as to form a membrane, and as they are subjected to mutual pressure, 
assume a polyhedral shape, which gives to the membrane a mosaic appear¬ 
ance. The central part of -the vitellus becomes filled with a clear fluid. 
A secondary membrane shortly appears within the first, and the two together 
constitute the external and internal blastodermic membranes. 

Germinal Area.—At about this period there is an accumulation of cells 
at a certain spot upon the surface of the blastodermic membranes which 
marks the position of the future embryo. This spot, at first circular, soon 
becomes elongated, and forms the primitive trace , around which is a clear 
space, the area pellucida , which is itself surrounded by a darker region, 
the area opaca. 

The primitive trace soon disappears, and the area pellucida becomes 
guitar-shaped; a new groove, the medullary groove, is now formed, which 
develops from before backward, and becomes the neural canal. 

Blastodermic Membranes.—The embryo, at this period, consists of ' 
three layers, viz.: the external and internal blastodermic membranes, and a 
middle membrane formed by a genesis of cells from their internal surfaces. 
These layers are known as the epiblast, mesoblast, and hypoblast. 

The epiblast gives rise to the central nervous system, the epidermis of 
the skin and its appendages, and the primitive kidneys. 

The ?nesoblast gives rise to the dermis, muscles, bones, nerves, blood¬ 
vessels, sympathetic nervous system, connective tissue, the urinary and 
reproductive apparatus, and the walls of the alimentary canal. 

The hypoblast gives rise to the epithelial lining of the alimentary canal 
and its glandular appendages, the liver and pancreas, and the epithelium 
of the respiratory tract. 

Dorsal Laminae.—As development advances, the true medullary 
groove deepens, and there arise two longitudinal elevations of the epiblast, 
the dorsal lamina , one on either side of the groove, which grow up, arch 
over, and unite so as to form a closed tube, the primitive central nervous 
system. 

The Chorda Dorsalis is a cylindrical rod running almost throughout 
the entire length of the embryo. It is formed by an aggregation of meso- 
blastic cells, and situated immediately beneath the medullary groove. 

Primitive Vertebrae.—On either side of the neural canal the cells of 
the mesoblast undergo a longitudinal thickening, which develops and ex- 


DEVELOPMENT OF ACCESSORY STRUCTURES. 


219 


tends around the neural canal and the chorda dorsalis, and forms the arches 
and bodies of the vertebrae. They become divided transversely into four¬ 
sided segments. 

The mesoblast now separates into two layers ; the external, joining with 
the epiblast, forms the somatopleure; the internal, joining with the hypo¬ 
blast, forms the splanchnopleure ; the space between them constituting the 
pleuroperitoneal cavity. 

Visceral Laminae.—The walls of the pleuro peritoneal cavity are 
formed by a downward prolongation of the somatopleure (the visceral 
lamina), which, as they extend around in front, pinch off a portion of the 
yelk sac (formed by the splanchnopleure), which becomes the primitive 
alimentary canal; the lower portion, remaining outside of the body cavity, 
forms the umbilical vesicle , which after a time disappears. 

Formation of Fetal Membranes.—The amnion appears shortly 
after the embryo begins to develop, and is formed by folds of the epiblast 
and external layer of the mesoblast, rising up in front and behind, and on 
each side; these amniotic folds gradually extend over the back of the 
embryo to a certain point, where they coalesce, and enclose a cavity, the 
amniotic cavity. The membranous partition between the folds disappears, 
and the outer layer recedes and becomes blended with the vitelline mem¬ 
brane, constituting the chorion , the external covering of the embryo. 

The Allantois.—As the amnion develops, there grows out from the 
posterior portion of the alimentary canal a pouch, or diverticulum, the 
allantois, which carries blood-vessels derived from the intestinal circulation. 
As it gradually enlarges, it becomes more vascular, and inserts itself be¬ 
tween the two layers of the amnion, coming into intimate contact with the 
external layer. Finally, from increased growth, it completely surrounds 
the embryo, and its edges become fused together. 

In the bird, the allantois is a respiratory organ, absorbing oxygen and 
exhaling carbonic acid; it also absorbs nutritious matter from the interior 
of the egg. 

Amniotic Fluid.—The amnion, when first formed, is in close contact 
with the surface of the ovum ; but it soon enlarges, and becomes filled 
with a clear, transparent fluid, containing, alburifin, glucose, fatty matters, 
urea, and inorganic salts. It increases in amount up to the latter period of 
gestation, when it amounts to about two pints. In the space between the 
amnion and allantois is a gelatinous material, which is encroached upon 
and finally disappears as the amnion and allantois come in contact, at about 
the fifth month. 


220 


HUMAN PHYSIOLOGY. 


The Chorion, the external investment of the embryo, is formed by a 
fusion of the original vitelline membrane, the external layer of the amnion, 
and the allantois. The external surface now becomes covered with villous 
processes, which increase in number and size by the continual budding 
and growth of club-shaped processes from the main stem, and give to the 
chorion a shaggy appearance. They consist of a homogeneous granular 
matter, and are penetrated by branches of the blood-vessels derived from 
the aorta. 

The presence of villous processes in the uterine cavity is proof positive 
of the previous existence of a fetus. They are characteristic of the 
chorion, and are found under no other circumstances. 

At about the end of the second month the villosities begin to atrophy 
and disappear from the surface of the chorion, with the exception of those 
situated at the points of entrance of the fetal blood-vessels, which occupy 
about one-third of its surface, where they continue to grow longer, become 
more vascular, and ultimately assist in the formation of the placenta; the 
remaining two-thirds of the surface loses its villi and blood-vessels, and 
becomes a simple membrane. 

The Umbilical Cord connects the fetus with that portion of the 
chorion which forms the fetal side of the placenta. It is a process of the 
allantois, and contains two arteries and a vein, which have a more or less 
spiral direction. It appears at the end of the first month, and gradually 
increases in length, until, at the end of gestation, it measures about twenty 
inches. The cord is also surrounded by a process of the amnion. 

Development of the Decidual Membrane.—The interior of the 
uterus is lined by a thin, delicate mucous membrane, in which are im¬ 
bedded immense numbers of tubules, terminating in blind extremities, the 
uterine tubules. At each period ^of menstruation the mucous membrane 
becomes thickened and vascular, which condition, however, disappears 
after the usual menstrual discharge. When the ovum becomes fecundated, 
the mucous membrane takes on an increased growth, becomes more hyper¬ 
trophied and vascular, sends up little processes, or elevations from its sur¬ 
face, and constitutes the decidua vera. 

As the ovum passes from the Fallopian tube into the interior of the 
uterus, the primitive vitelline membrane, covered with villosities, becomes 
entangled with the processes of the mucous membrane. A portion of the 
decidua vera then grows up on all sides and encloses the ovum, forming 
the decidua reflexa, while the villous processes of the chorion insert them¬ 
selves into the uterine tubules, and in the mucous membrane between 
them. 


DEVELOPMENT OF ACCESSORY STRUCTURES. 


221 


As development advances the decidua reflexa increases in size, and at 
about the end of the fourth month comes in contact with the decidua vera, 
with which it is ultimately fused. 

The Placenta.—Of all the embryonic structures, the placenta is the 
most important. It is formed in the third month, and then increases in size 
until the seventh month, when a retrogressive metamorphosis takes place 
until its separation during labor, at which time it is of an oval or rounded 
shape, and measures from seven to nine inches in length, six to eight 
inches in breadth, and weighs from fifteen to twenty ounces. It is most 
frequently situated at the upper and posterior part of the inner surface of 
the uterus. 

The placenta consists of two portions, a fetal and a maternal. 

The fetal portion is formed by the villi of the chorion, which, by devel¬ 
oping, rapidly increase in size and number. They become branched and 
penetrate the uterine tubules, which enlarge and receive their many ramifi¬ 
cations. The capillary blood-vessels in the anterior of the villi also enlarge 
and freely anastomose with each other. 

The maternal portion is formed from that part of the hypertrophied and 
vascular decidual membrane between the ovum and the uterus, the decidua 
serotina. As the placenta increases in size, the maternal blood-vessels 
around the tubules become more and more numerous, and gradually fuse 
together, forming great lakes, which constitute sinuses in the walls of the 
uterus. 

As the latter period of gestation approaches, the villi extend deeper into 
the decidua, while the sinuses in the maternal portion become larger and 
extend further into the chorion. Finally, from excessive development of 
the blood-vessels, the structures between them disappear, and as their walls 
come in contact, they fuse together, so that, ultimately, the maternal and 
fetal blood are only separated by a thin layer of a homogeneous substance. 
When fully formed, the placenta consists principally of blood-vessels inter¬ 
lacing in every direction. The blood of the mother passes from the uterine 
vessels into the lakes surrounding the villi ; the blood from the child flows 
from the umbilical arteries into the interior of the villi; but there is not at 
any time an intermingling of blood, the two being separated by a delicate 
membrane formed by a fusion of the walls of the blood-vessels and the 
walls of the villi and uterine sinuses. 

The function of the placenta, besides nutrition, is that of a respiratory 
organ , permitting the oxygen of the maternal blood to pass by osmosis 
through the delicate placental membrane into the blood of the fetus; at 
the same time permitting the carbonic acid and other waste products, the 


222 


HUMAN PHYSIOLOGY. 


result of nutritive changes in the fetus, to pass into the maternal blood, and 
so to be carried to the various eliminating organs. 

Through the placenta also passes all the nutritious materials of the 
maternal blood which are essential for the development of the embryo. 

At about the middle of gestation there develops beneath the decidual 
membrane a new mucous membrane, destined to perform the functions of 
the old when it is extruded from the womb, along with the other embryonic 
structures, during parturition. 


DEVELOPMENT OF THE EMBRYO. 

Nervous System.—The cerebro-spinal axis is formed within the me¬ 
dullary canal by the development of cells from its inner surfaces, which 
as they increase fill up the canal, and there remains only the central canal 
of the cord. The external surface gives rise to the dura mater and pia 
mater. The neural canal thus formed is a tubular membrane ; it terminates 
posteriorly in an oval dilatation, and anteriorly in a bulbous extremity, 
which soon becomes partially contracted, and forms the anterior, middle 
and posterior cerebral vesicles, from which are ultimately developed the 
cerebrum, the corpora quadrigemina, and medulla oblongata, respectively. 

The anterior vesicle soon subdivides into two secondary vesicles, the 
larger of which becomes the hemispheres, the smaller, the optic thalami; 
the posterior vesicle also divides into two, the anterior becoming the cere¬ 
bellum, the posterior the pons Varolii and medulla oblongata. 

About the seventh week the straight chain of cerebral vesicles becomes 
curved from behind forward and forms three prominent angles. As devel¬ 
opment advances, the relative size of the encephalic masses changes. The 
cerebrum developing more rapidly than the posterior portion of the brain, 
soon grows backward and arches over the optic thalami and the tubercula 
quadrigemina; the cerebellum overlaps the medulla oblongata. 

The surface of the cerebral hemispheres is at first smooth, but at about 
the fourth month begins to be marked by the future fissures and convolutions. 

The Eye is formed by a little bud projecting from the side of the 
anterior vesicle. It is at first hollow, but becomes lined with nervous 
matter, forming the optic nerve and retina ; the remainder of the cavity is 
occupied by the vitreous body. The anterior portion of the pouch becomes 
invaginated and receives the crystalline lens , which is a product of the 
epiblast, as is also the cornea. The iris appears as a circular membrane 
without a central aperture, about the seventh week; the eyelids are formed 
between the second and third months. 


DEVELOPMENT OF THE EMBRYO. 


223 


The Internal Ear is developed from the auditory vesicle, budding from 
the third cerebral vesicle; the membranous vestibule appears first, and from 
it diverticula are given off, which become the semicircular canals and 
cochlea. 

The cavity of the tympanum, the Eustachian tube, and the external 
auditory canal are the remains of the first branchial cleft, the cavity of this 
cleft being subdivided into the tympanum and external auditory meatus by 
the membrana tympani. 

The Skeleton.—The chorda dorsalis, the primitive part of the vertebral 
column, is a cartilaginous rod situated beneath the medullary groove. It is 
a temporary structure, and disappears as the true bony vertebrae develop. 
On either side are the quadrate masses of the mesoblast, the primitive ver¬ 
tebrae, which send processes upward and around the medullary groove, and 
downward and around the chorda dorsalis, forming in these situations the 
arches and bodies of the future vertebrae. 

More externally the outer layers of the mesoblast and epiblast arch down¬ 
ward and forward, forming the ventral laminae, in which develop the 
muscles and bones of the abdominal walls. 

The true cranium is an anterior development of the vertebral column, and 
consists of the occipital, parietal, and frontal segments, which correspond to 
the three cerebral vesicles. The base of the cranium consists, at this period, 
of a cartilaginous rod on either side of the anterior extremity of the chorda 
dorsalis, in which three centers of ossification appear, the basi-occipital, the 
basi-sphenoidal, and the pre-sphenoidal. They ultimately develop into the 
basilar process of the occipital bone and the body of the sphenoid. 

Th t entire skeleton is at first either membranous or cartilaginous. At the 
beginning of the second month centers of ossification appear in the jaws and 
clavicle; as development advances, the ossific points in all the future bones 
extend, until ossification is completed. 

The limbs develop from four little buds projecting from the sides of the 
embryo, which, as they increase in length, separate into the thigh, leg, and 
foot, and the arm, forearm, and hand; the extremities of the limbs undergo 
subdivision, to form the fingers and toes. 

Face and Visceral Arches.—In the facial and cervical regions the 
visceral laminae send up three processes, the visceral arches , separated by 
clefts, the visceral clefts. 

The first , or the mandibular arches , unite in the median line to form the 
lower jaw, and superiorly form the malleus. A process jutting from its 
base grows forward, unites with the fronto-nasal process growing from 


224 


HUMAN PHYSIOLOGY. 


above, and forms the upper jaw. When the superior maxillary processes 
fail to unite, there results the cleft-palate deformity; if the integument also 
fails to unite, there results the hare-lip deformity. The space above the 
mandibular arch becomes the mouth. 

The second arch develops the incus and stapes bones, the styloid process 
and ligament, and the lesser cornua of the hyoid bone. The cleft between 
the first and second arches partially closes up, but there remains an open¬ 
ing at the side which becomes the Eustachian tube, tympanic cavity, and 
external auditory meatus. 

The third arch develops the body and greater cornu of the hyoid 
bone. 

Alimentary Canal and its Appendages.—The alimentary canal is 
formed by a pinching off of the yelk sac by the visceral plates as they grow 
downward and forward. It consists of three distinct portions, the fore gut, 
the hind gut, and the central part, which communicates for some time with 
the yelk sac. It is at first a straight tube, closed at both extremities, lying 
just beneath the vertebral column. The canal gradually increases in 
length, and becomes more or less convoluted ; at its anterior portion two 
pouches appear, which become the cardiac and pyloric extremities of the 
stomach. At about the seventh week the inferior extremity of the intestine 
is brought into communication with the exterior, by an opening, the anus. 
Anteriorly the mouth and pharynx are formed by an involution of epiblast, 
which deepens until it communicates with the fore gut. 

The liver appears as a slight protrusion from the sides of the alimentary 
canal, about the end of the first month; it grows very rapidly, attains a 
large size, and almost fills up the abdominal cavity. The hepatic cells are 
derived from the intestinal epithelium, the vessels and connective tissue 
from the mesoblast. 

The pancreas is formed by the hypoblastic membrane. It originates in 
two small ducts budding from the duodenum, which divide and subdivide, 
and develop the glandular structure. 

The lungs are developed from the anterior part of the esophagus. At 
first a small bud appears, which, as it lengthens, divides into two branches; 
secondary and tertiary processes are given off these, which form the bron¬ 
chial tubes and air cells. The lungs originally extended into the abdomi¬ 
nal cavity, but become confined to the thorax by the development of the 
diaphragm. 

The bladder is formed by a dilatation of that portion of the allantois 
remaining within the abdominal cavity. It is at first pear-shaped, and 
communicates with the intestine, but later becomes separated, and opens 


DEVELOPMENT OF THE EMBRYO. 


225 


exteriorly by the urethra. It is attached to the abdominal walls by a 
rounded cord, the urachus, the remains of a portion of the allantois. 

Genito-urinary Apparatus.—The Wolffian bodies appear about the 
thirteenth day, as long, hollow tubes running along each side of the primi¬ 
tive vertebral column. They are temporary structures, and are sometimes 
called the primordial kidneys. The Wolffian bodies consist of tubules 
which run transversely and are lined with epithelium ; internally they be¬ 
come invaginated to receive tufts of blood-vessels; externally they open 
into a common excretory duct, the duct of the Wolffian body , which unites 
with the duct of the opposite body, and empties into the intestinal canal 
at a point opposite the allantois. On the outer side of the Wolffian body 
there appears another duct, the duct of Muller, which also opens into the 
intestine. 

Behind the Wolffian bodies are developed the structures which become 
either the ovaries or testicles. In the development of the female, the 
Wolffian bodies and their ducts disappear; the extremities of the Mullerian 
ducts dilate and form the fimbriated extremity of the Fallopian tubes, while 
the lower portions coalesce to form the body of the uterus and vagina, 
which now separate themselves from the intestine. 

In the development of the male, the Mullerian ducts atrophy, and the 
ducts of the Wolffian body ultimately form the epididymis and vas defer¬ 
ens. About the seventh month the testicles begin to descend, and by the 
ninth month have passed through the abdominal ring into the scrotum. 

The kidneys are developed out of the Wolffian bodies. They consist of 
little pyramidal lobules, composed of tubules which open at the apex into 
the pelvis. As they pass outward they become convoluted and cup-shaped 
at their extremities, receive a tuft of blood-vessels, and form the Malpig¬ 
hian bodies. 

The ureters are developed from the kidneys, and pass downward to be 
connected with the bladder. 

The Circulatory Apparatus assumes three different forms at different 
periods of life, all having reference to the manner in which the embryo 
receives nutritious matter and is freed of waste products. 

The vitelline circulation appears first and absorbs nutritious material 
from the vitellus. It is formed by blood-vessels which emerge from the 
body and ramify over a portion of the vitelline membrane, constituting the 
area vasculosa. The heart, lying in the median line, gives off two arches 
which unite to form the abdominal aorta, from which two large arteries 
are given off, passing into the vascular area; the venous blood is returned 


226 


HUMAN PHYSIOLOGY. 


by veins which enter the heart. These vessels are known as the omphalo¬ 
mesenteric arteries and veins. The vitelline circulation is of short dura¬ 
tion in the mammals, as the supply of nutritious matter in the vitellus soon 
becomes exhausted. 

The placental circulation becomes established when the blood-vessels 
in the allantois enter the villous processes of the chorion and come into 
close relationship with the maternal blood-vessels. This circulation lasts 
during the whole of intra-uterine life, but gives way at birth to the adult 
circulation, the change being made possible by the development of the cir¬ 
culatory apparatus. 

The Heart appears as a mass of cells coming off from the anterior por¬ 
tion of the intestine; its central part liquefies, and pulsations soon begin. 
The heart is at first tubular, receiving posteriorly the venous trunks and 
giving off anteriorly the arterial trunks. It soon becomes twisted upon 
itself, so that the two extremities lie upon the same plane. 

The heart now consists of a single auricle and a single ventricle. A 
septum growing from the apex of the ventricle divides it into two cavities, 
a right and a left. The auricles also become partly separated by a septum 
which is perforated by the foramen ovale. The arterial trunk becomes 
separated by a partition into two canals, which become, ultimately, the 
aorta and pulmonary artery. The auricles are separated from the ventricles 
by incomplete septa, through which the blood passes into the ventricles. 

Arteries. —The aorta arises from the cephalic extremity of the heart and 
divides into two branches, which ascend, one on each side of the intestine, 
and unite posteriorly to form the main aorta; posteriorly to these first aortic 
arches, four others are developed, so that there are five altogether running 
along the visceral arches. The two anterior soon disappear. The third 
arch becomes the internal carotid and the external carotid; a part of the 
fourth arch , on the right side, becomes the subclavian artery, and the 
remainder atrophies and disappears, but on the left side it enlarges and 
becomes the permanent aorta ; the fifth arch becomes the pulmonary artery 
on the left side. The communication between the pulmonary artery and 
the aorta, the ductus arteriosus , disappears at an early period. 

Veins. —The venous system appears first as two short, transverse veins, 
the canals of Cuvier, formed by the union of the vertebral veins and the 
cardinal veins, which empty into the auricle. The inferior vena cava is 
formed as the kidneys develop, by the union of the renal veins, which, in a 
short time, receive branches from the lower extremities. The subclavian 
veins join the jugular as the upper extremities develop. The heart descends 
in the thorax, and the canals of Cuvier become oblique ; they shortly com- 


DEVELOPMENT OF THE EMBRYO. 


227 


municate by a transverse duct, which ultimately becomes the left innomi¬ 
nate vein. The left canal of Cuvier atrophies and becomes a fibrous cord. 
A transverse branch now appears, which carries the blood from the left 
cardiac vein into the right, and becomes the vena azygos minor; the right 
cardinal vein becomes the vena azygos major. 

Circulation of Blood in the Fetus.—The blood returning from the 
placenta, after having received oxygen, and being freed from carbonic 
acid, is carried by the umbilical vein to the under surface of the liver; here 
a portion of it passes through the ductus venosus into the ascending vena 
cava, while the remainder flows through the liver and passes into the vena 
cava by the hepatic veins. When the blood is emptied into the right 
auricle, it is directed by the Eustachian valve through the foramen ovale, 
into the left auricle, thence into the left ventricle, and so into the aorta to 
all parts of the system. The venous blood returning from the head and 
upper extremities is emptied, by the superior vena cava, into the right 
auricle, from which it passes into the right ventricle, and thence into the 
pulmonary artery. Owing to the condition of the lung, only a small por¬ 
tion flows through the pulmonary capillaries, the greater part passing 
through the ductus arteriosus, which opens into the aorta at a point below 
the origin of the carotid and subclavian arteries. The mixed blood now 
passes down the aorta, to supply the lower extremities, but a portion of 
it is directed, by the hypogastric arteries, to the placenta, to be again 
oxygenated. 

At birth, the placental circulation gives way to the circulation of the 
adult. As soon as the child begins to breathe, the lungs expand, blood 
flows freely through the pulmonary capillaries, and the ductus arteriosus 
begins to contract. The foramen ovale closes about the tenth day. The 
umbilical vein, the ductus venosus, and the hypogastric arteries become 
impervious in several days, and ultimately form rounded cords. 


228 


HUMAN PHYSIOLOGY. 


TABLE OF PHYSIOLOGICAL CONSTANTS. 


Mean height of male, 5 feet 6^ inches ; of female, 5 feet 2 inches. 

Mean weight of male, 145 pounds; of female, 121 pounds. 

Number of chemical elements in the human body ; from 16 to 18. 
Number of proximate principles in the human body; about 100. 

Amount of water in the body weighing 145 pounds ; 108 pounds. 

Amount of solids in the body weighing 145 pounds; 36 pounds. 

Amount of food required daily; 16 ounces meat, 10 ounces of bread, 3^ 
ounces of fat, 52 ounces of water. 

Amount of saliva secreted in 24 hours ; about 3^ pounds. 

Function of saliva ; converts starch into glucose. 

Active principle of saliva ; ptyalin. 

Amount of gastric juice secreted in 24 hours; from 8 to 14 pounds. 
Functions of gastric juice ; converts albumin into albuminose. 

Active principles of gastric juice ; pepsin and hydrochloric acid. 
Duration of digestion ; from 3 to 5 hours. 

Amount of intestinal juice secreted in 24 hours ; about 1 pound. 

Function of intestinal juice ; converts starch into glucose. 

Amount of pancreatic juice secreted in 24 hours; about 1 % pounds. 

Active principles of pancreatic juice; trypsin, amylopsin, and 
steapsin. 

{ I. Emulsifies fats. 

2. Converts albumin into albuminose. 

3. Converts starch into glucose. 

Amount of bile poured into the intestines daily; about 2^4 pounds, 
f 1. Assists in the emulsification of fats. 

I 2. Stimulates the peristaltic movements, 
j 3. Prevents putrefactive changes in the food. 

* ( 4. Promotes the absorption of the fat. 

Amount of blood in the body; from 16 to 18 pounds. 

Size of red corpuscles ; of an inch. 

Size of white corpuscles ; of an inch. 

Shape of red corpuscles ; circular biconcave discs. 

Shape of white corpuscles ; globular. 

Number of red corpuscles in a cubic millimeter of blood (the cubic of 
an inch); 5,000,000. 



TABLE OP' PHYSIOLOGICAL CONSTANTS. 


229 


Function of red corpuscles ; to carry oxygen from the lungs to the tissues. 
Frequency of the heart’s pulsations per minute; 72 on the average. 
Velocity of the blood movement in the arteries; about 16 inches per 
second. 

Length of time required for the blood to make an entire circuit of the 
vascular system; about 20 seconds. 

Amount of air passing in and out of the lungs at each respiratory act; 
from 20 to 30 cubic inches. 

Amount of air that can be taken into the lungs on a forced inspiration; 
110 cubic inches. 

Amount of reserve air in the lungs after an ordinary expiration; 100 cubic 
inches. 

Amount of residual air always remaining in the lungs; about 100 cubic 
inches. 

Vital capacity of the lungs; 230 cubic inches. 

Entire volume of air passing in and out of the lungs in 24 hours; about 
400 cubic feet. 

Composition of the air; nitrogen, 79.19; oxygen, 20.81, per 100 parts. 
Amount of oxygen absorbed in 24 hours ; 18 cubic feet. 

Amount of carbonic acid exhaled in 24 hours; 14 cubic feet. 
Temperature of the human body at the surface; 98^° F. 

Amount of urine excreted daily; from 40 to 50 ounces. 

Amount of urea excreted daily ; 512 grains. 

Specific gravity of urine ; from 1.015 to 1.025. 

Number of spinal nerves ; 31 pairs. 

Number of roots of origin; two; 1st, anterior, motor; 2d, posterior, 
sensory. 

Rate of transmission of nerve force ; about 100 feet per second. 

Number of cranial nerves ; 12 pairs. 

1. Olfactory, or 1st pair. 

2. Optic, or 2d pair. 

3. Auditory, or 8th pair. 

4. Chorda tympani for anterior % of tongue. 

5. Branches of glosso-pharyngeal, or 8th 
pair, for posterior of tongue. 

Motor nerves to eyeball and accessory structures ; motor oculi, or 3d 
pair ; pathetic, or 4th pair; abducens, or 6th pair. 

Motor nerves to facial muscles ; portio dura, facial, or 7th pair. 

Motor nerve to tongue ; hypoglossal, or 12th pair. 

Motor nerve to laryngeal muscles ; spinal accessory, or nth pair. 


Nerves of special sense: 1 




230 


HUMAN PHYSIOLOGY. 


Sensory nerve of the face; trifacial, or 5th pair. 

Sensory nerve of the pharynx; glosso-pharyngeal, or 9th pair. 

Sensory nerves of the lungs, stomach, etc; pneumogastric, or 10th 
pair. 

Length of spinal cord; 16 to 18 inches, weight 1 ounces. 

Point of decussation of motor fibers; at the medulla oblongata. 

Point of decussation of sensory fibers; throughout the spinal cord. 

Function of antero-lateral columns of spinal cord; transmit motor 
impulses from the brain to the muscles. . 

Functions of the posterior columns; assist in the coordination of mus¬ 
cular movements. 

Functions of the medulla oblongata; controls the functions of insaliva¬ 
tion, mastication, deglutition, respiration, circulation, etc. 

Functions of the corpora quadrigemina ; physical centers for sight. 

Functions of the corpora striata; centers for motion. 

Functions of the optic thalami; centers for sensation. 

Function of the cerebellum ; center for the coordination of muscular 
movement. 

Function of the cerebrum ; center for intelligence, reason, and will. 

Center for articulate language; 3d frontal convolution on the left side of 
cerebrum. 

Number of coats to the eye ; three; 1st, cornea and sclerotic; 2d, choroid; 
3d, retina. 

Function of iris ; regulates the amount of light entering the eye. 

Function of crystalline lens; refracts the rays of light so as to form an 
image on the retina. 

Function of retina; receives the impressions of light. 

Function of membrana tympani; receives and transmits waves of sound 
to internal ear. 

Function of Eustachian tube; regulates the passage of air into and from 
the middle ear. 

Function of semicircular canals; assist in maintaining the equipoise of 
the body. 

Function of the cochlea; appreciates the shades and combinations of 
musical tones. 

Size of human ovum ; yi-g- of an inch in diameter. 

Size of spermatozoa; °f an length. 

Function of the placenta ; acts as a respiratory and digestive organ for the 
fetus. 

Duration of pregnancy ; 280 days. 


TABLE SHOWING RELATION OF WEIGHTS AND 
MEASURES OF THE METRIC SYSTEM TO APPROX¬ 
IMATE WEIGHTS AND MEASURES OF THE U. S. 


One Myriameter 
One Kilometer 
One Hectometer 
One Decameter 

One Meter 

One Decimeter 
One Centimeter 

One Millimeter 

One Myriagram 
One Kilogram 
One Hectogram 
One Decagram 

One Gram 

One Decigram 

• One Centigram 

One Milligram 

One Myrialiter 
One Kiloliter. 
One Hectoliter 


One Decaliter 


One Liter 


One Deciliter 


One Centiliter 


One Milliliter 


MEASURES OF LENGTH. 
= 10,000 meters = 

,= 1,000 “ =J 

= IOO “ » == 

= IO “ = 

{ the ten millionth part of a 
quarter of the Meridian of 
the Earth 
= the tenth part of one meter — 

_ f the one hundredth part of \ _ 

\ one meter J 

_ j the one thousandth part of |_ 


\ one meter 

WEIGHTS. 

= 10,000 grams = 

= 1,000 “ = 

== IOO “ = 

= IO “ = 

_ f the weight of a cubic centi-1 _ 

\ meter of water at 4 0 C. J 
= the tenth part of agram = 

_ f the hundredth part of one 1 _ 

“ l gram J — 

_ f the thousandth part of one \_ 

— \ gram J 


1 gram 

MEASURES OF CAPACITY. 

{ 10 cubic Meters or the) 
measure of 10 Milliers of >■ = 
water J 

_ j 1 cubic Meter or the meas-1 _ 

\ ure of I Millier of water. / 

i ioo cubic Decimeters or ) 
the measure of 1 Quintal >• = 
of water J 

{ 10 cubic Decimeters or) 
the measure of 1 Myria- 1 = 
gram of water J 

{ 1 cubic Decimeter or the ) 
measure of I Kilogram l- = 
of water J 

{ 100 cubic Centimeters or 
the measure of 1 Hecto¬ 
gram of water 

{ 10 cubic Centimeters or 
the measure of one Deca¬ 
gram of water 

{ 1 cubic Centimeter or the | 
measure of 1 Gram of > = 
water J 


32800. feet. 

3280. “ 

328.0 “ 

32.80 “ 

39.368 inches. 
3.936 
•393 (1) 

•°39 (#7) “ 

26^ pounds Troy. 
2 % “ “ 

3^" ounces “ 

2 y 2 drachms “ 

15-434 grains. 
1-543 ( 1 ^) “ 

•I 54 (> 4 ) 

• OI 5 Wt) 

2600. gallons. 

260. “ 

26. “ 

2.6 “ 

2.1 pints. 

3.3 ounces. 

2.7 drachms. 
16.2 minims. 





INDEX 


PAGE 

A BDUCENS NERVE, .... 142 
Aberration, chromatic, .... 200 

——, spherical,.200 

Absorption,. 76 

-by the lacteals,. 80 

-by the blood-vessels, .... 81 

-of oxygen in respiration, . . . 103 

Accommodation of the eye, .... 199 
Adipose tissue, uses of in the body, . 36 

Adult circulation, establishment of at 

birth,.227 

Air, atmospheric, composition of, . 103 


•, amount exchanged in respira 


tion,. 102 

-, changes in, during respiration 103 

Albumin, uses of, in the body, ... 37 

Albuminoid substances,. 37 

Alcohol, action of,. 60 

Alimentary principles, classification 

of, .. 

-, albuminous principles, 

-, saccharin principles, . 

-, oleaginous principles, . 

inorganic principles, 


59 

59 

60 
60 
60 

224 


Alimentary canal, development of, . 
Allantois, development and function 

of,.219 

Amnion, formation of,.219 

Animal heat,.105 

Anterior columns of spinal cord, . . 154 

Area, germinal,. 218 

Arteries, properties of,. 94 

Articulations,. 19 

-, axial,. 20 

Asphyxia,.105 

Astigmatism,.200 

Axis, cerebro-spinal,.152 

-cylinder of nerves,.131 


RILE,. 74 

Bladder, urinary, . . . ... 117 

Blastodermic membranes,.218 

Blood,. 83 

-, composition of plasma, ... 84 

-, coagulation of,. 87 

-, coloring matter of,. 86 

-, changes in, during respira¬ 
tion, .105 

-, circulation of, . .. 89 

-, rapidity of flow in arteries, . 96 

-, rapidity of flow in capillaries, 96 

-, pathological conditions of, . . 89 


PAGE 

Blood, corpuscles,. 85 

-, origin of,. 85 

- pressure,. 95 

Bone, structure of, .. 17 

Burdach, column of,.155 

pANALS OF CUVIER, .... 226 

^ Capillary blood-vessels, .... 96 

Capsule, internal,.170 

-, external,.170 

Cartilage,. 18 

Caudate nucleus,.170 

Cells, structure of,. 25 

-, manifestation of life by, ... 26 

- of antefior horns of gray 

matter, 155.155 

Center for articulate language, . . . 182 

Cerebrum,.173 

-, fissures and convolutions, . . 174 

-, functions of,.377 

-, localization of functions, . . 180 

-, motor area of,.180 

-, special centers of, . . . . 181 

Cerebellum,.171 

-, forced movements of, • . . . 172 

Cerebral vesicles of embryo, .... 222 

Chemical composition of human body 31 

- elements, proximate quantity 

of in body,. 39 

Chorda dorsalis,.218 

- tympani nerve, course and 

function of,.145 

Chorion,. ... 220 

Chyle,. 82 

Ciliary muscle,.199 

Circulation of blood, ■ . 88 

Claustrum,.170 

Cochlea,.' . . . . 208 

Columns of spinal cord,.154 

Corium,.327 

Corpora Wolffiana,.225 

-quadrigemina,.169 

Corpus luteum,.214 

-striatum,.170 

Corti, organ of,.209 

Cranial nerves,.138 

Crura cerebri,.368 

Crystalline lens,.196 

TAECIDUAL MEMBRANE, . 220 

Decussation of motor and sen¬ 
sory fibers,.156 


233 










































































































234 


INDEX 


PAGE 


Deglutition*. 67 

-, nervous circle of,.166 

Development of accessory structures 

of embyro,.217 

Digestion,. 62 

Ductus arteriosus, 226 

-venosus,.226 


'C'A.R ..202 

Electrotonus,.137 

Embryo, development of,.222 

Endolymph, .209 

Epidermis,.127 

Epididymis,.216 

Eustachian tube,.205 

Excretion,. 114 

Eye, ..191 

-■, refracting apparatus of, . . . 197 

-, blind spot of,.201 


PACIAL NERVE.142 

*• - paralysis, symptoms of, 142 

Fallopian tubes,.213 

Feces,. 75 

Fat, uses of in the body,* . ... 36 

Female organs of generation. .... 213 
Fissures and convolutions of brain, . 174 

Food,. 57 

-, percentage composition of, . 61 

-, daily amount required, ... 61 

-, albuminous principles of, . . 59 

-, saccharin principles of. . . . 60 

-, oleaginous principles of, . . . 60 

-, inorganic principles of, ... 60 

Fovea centralis,.201 

r'ALVANIC CURRENTS, EF- 

feet on nerves,.137 

Ganglia,.185 

-, ophthalmic,.185 

-, Gasserian,.185 

-, spheno-palatine.185 

-, otic,.185 

-, sub-maxillary,.185 

-, semilunar,. . . 186 

Gases of the intestine. 75 

-, condition of, in blood, . . . 104 

Gastric juice,. 69 

-, action of, •. 70 

Generation, male organs of,.216 

- -, female organs of,.213 

Globules of the blood,. 84 

-of the lymph.8r 

Glomeruli of the kidneys,.117 

Glosso-pharyngeal nerve,.147 

Glottis, respiratory movements of, . 101 

Glycogen,.125 

Glycogenic function of the liver, . . 125 

Goll, column of,.154 

Graafian follicles,.213 

Gray matter of nervous system, . . 130 


FAGE 


UAIR,.127 

Hemoglobin,. 86 

Hearing, sense of,.202 

Heart,.89 

-, valves of,. 90 

-, sounds of,. 92 

-, influence of pneumogastric 

nerve upon,. 94 

Heart, ganglia of,. 94 

-, force exerted by left ventricle, 93 

-, work done by. 93 

-, course of blood through, . . 91 

-, influence of nervous system 

upon,. 93 

Hyaloid membrane,.191 

Hypermetropia,.200 

Hypoglossal nerve,.151 

TNCUS BONE,.204 

Insalivation,. 64 


Inspiration, movements of thorax in, 100 

Internal capsule,.170 

-, results of injury to, . . . . 170 

Intestinal juice,. 72 

Iris,.193 

-, action of,.200 

Island of Red,. 176 


.114 

of urine by . 121 


T ABYRINTH OF INTERNAL 

ear, . ..208 

-, function of cochlea,.208 

-, function of semicircular canals 207 

Language, articulate, center for, . . 182 

Larynx, ... 210 

Lateral columns of spinal cord, . . . 154 
Laws of muscular contraction, . . . 138 

Lens, crystalline,.196 

Lime phosphate. 33 

Liver,.• 122 

-, secretion of bile by, .... 124 

-, glycogenic function of, . . . 125 

-, elaboration of blood, .... 126 

-cells,.123 

Localization of functions in cerebrum 180 

Lungs,. 98 

-, changes in blood while passing 

through,.105 

Lymph,. 81 

Lymphatic glands,. 78 

-vessels, origin and c.ourse of, • 77 


MAMMARY GLANDS, ... in 

Malleus bone,.203 

Mastication. 63 

-, nervous circle of,. 63 

-, muscles of,.• . . . 63 

Medulla oblongata,.164 


J£IDNEYS 


excretion 


























































































































INDEX. 


235 


PAGE 

Medulla oblongata, properties and 


functions of,.163 

Membrana basilaris,.209 

-tympani,.203 

Menstruation,.214 

Middle ear, ..203 

Milk,. hi 

Motor centers of cerebrum,.180 

Muscles, properties of,. 39 

Myopia, ..2co 


MERVE, OLFACTORY, ... 139 

-, optic,.139 

-, motor oculi,.141 

-, pathetic, .141 

-, trigeminal,.143 

-, abducens,.142 

-, facial,.145 

-, auditory,.146 

-, glosso-pharyngeal,.147 

-. pneumogastric,.148 

-, spinal accessory,.150 

-, hypoglossal,.151 

-cells, structure of,.130 

-fibers, terminations of, ... . 132 

-force, rate of transmission of, . 136 

-roots, function of anterior and 

posterior,.155 


Nerves, centrifugal and centripetal, 


, I 33 > x 34 

-, cranial,.138 

-, decussation of motor and sen¬ 
sory.156 

-, vaso-motor,.166 

-, properties and functions of, . 133 

-, spinal,.155 

Nervous system,.130 

-, white and gray matter of, . . 131 

•-, cerebro-spinal,.130 

-, sympathetic,.184 

Nucleus caudatus,.170 

- lenticularis,.170 


QLFACTORY NERVES, . . . 

Ophthalmic ganglion,. 

Optic nerves,. 

-, thalamus,.. . 

-functions of,. 

Organs of Corti,. 

Otic ganglion,. 

Ovaries,. 

Ovum,. 

-, discharge of from the ovary, . 

Oxygen, absorption of by hemoglobin 


i39 

185 

* 39 "" 
170 

209 

185 

213 

213 

214 
86 


OACINIAN CORPUSCLES, . 133 

Pancreatic juice,. 73 

Patheticus nerve,.141 

Peptones,. 70 

Perilymph,.208 

Perspiration,.129 

Petrosal nerves, large and small, . . 146 
Phonation,.211 


PAGE 


Physiology, definition of,. 

Placenta, formation and function of, . 

Pleura, . 

Pneumogastric nerve,. 

Pons varolii, . .. 

Portal vein,. 

Posterior columns of spinal cord, . . 

-—, functions of,. 

Prehension,. 

Presbyopia,. 

Pressure of blood in arteries, .... 

Proximate principles,. 

-, inorganic, .. 

-, organic, non-nitrogenized, . 

-, organic, nitrogenized, . . . . 

-, of waste,. 

-quantity of chemical elements 

in body,. 

Ptyalin,. 

Pulse,. 

Pyramidal tracts,. 


9 

218 

99 

148 

168 

80 


*59 
1 

200 


59 

63 


95 

32 

32 

34 

36 

38 


95 

x 56 


T?ED CORPUSCLES OF 


blood,. 85 

Reflex movements of spinal cord, . . 160 

-action, laws of,.161 

Reproduction,.213 

Respiration,. 98 

-, movements of,.100 

-, nervous mechanism of, . . . 101 

-, types of,.102 

-, nervous circle of,.167 

Retina,.194 


OALIVA,. 

^ Sebaceous glands,. 


.... 65 

. . !28 

Secretion,.108 

Semicircular canals,.208 

Semen,.217 

Sight, sense of,.191 

Skeleton,. 11 

-, appendicular,.• . 15 

Skin,.127 

-, relative sensibility of, ... . 188 

Smell, sense of,.191 

Sounds of heart,. 92 

Spermatozoa,.217 

Spheno-palatine ganglion, ... . 185 

Spinal accessory nerve,.150 

Spinal cord,.153 

-, membranes of.153 

-, structure of white matter, . . 154 

-, structure of gray matter, . . 155 

-, properties of,.158 

-, function of as a conductor, 159 

-, as an independent center, . . 159 

-, decussation of motor and sen¬ 
sory fibers,. 156 

-, reflex action of,.160 

-, special centers of,.162 

-, paralysis, from injuries of, . . 163 

-nervesj origin of,.156 

-, course of anterior and posterior 

roots of,.156 














































































































































236 


INDEX. 


PAGE 

Spleen,.113 

Starvation, phenomena of,. 58 

Stomach,. 67 

Submaxillary ganglion,.185 

Sugar, uses of, in the body, .... 60 

Supra-renal capsules,.114 

Sudoriparous glands,.128 

Sympathetic nervous system, .... 184 
-, properties and functions of, . 186 

qPASTE, SENSE OF,.189 

-, nerve of,.190 

Teeth,. 25 

Tensor tympani muscle,.207 

Testicles,.216 

Thoracic duct,. 78 

Thorax, enlargement of, in inspiration 100 

Tissues, classification of,. 28 

Tongue,. 189 

-, motor nerve of,.190 

-■, sensory nerve of,.190 

Touch, sense of,.188 

Tiirck, column of,.156 


U MBILICAL CORD, 

Urea,. 


PAGE 

Uric acid,.120 

Urine,.118 

-, composition of,.119 

-, average quantity of constitu¬ 
ents secreted daily,.119 

Urination, nervous mechanism of, . 118 
Uterus,.154 

UAPOR, WATERY, OF 

v breath,.104 

Vascular glands.1x3 

-system, development of, . . . 225 

Vaso-motor nerves, origin of, ... . 166 

Veins,. 96 

Vesiculae seminales,.216 

Vision, physical center for,.169 

-, psychical center for, .... 183 

Vital capacity of lungs,.102 

Vocal cords.211 

Voice,.210 


\X 7 ATER, AMOUNT OF IN 

vv body,. 33 

Wolffian bodies,.225 












































CATALOGUE No. 7. 


NOVEMBER, 1893. 


BOOKS 

FOR 

STUDENTS, 

INCLUDING THE 

? QUIZ-COMPENDS ? 


CONTENTS. 


New Series of Manuals, 

PAGE 

2 , 3 , 4,5 

Anatomy, 

. 6 

Biology, 

. n 

Chemistry, . 

Children’s Diseases, . 

. 6 

• 7 

Dentistry, . ! 

. 8 

Dictionaries, 

8 , 16 

Eye Diseases, 
Electricity, . 

. 8 

• 9 

Gynsecology, 

. 10 

Hygiene, 

• 9 

Materia Medica, . 

• 9 

Medical Jurisprudence, 

. 10 

Nervous Diseases, 

. 10 


PAGE 

Obstetrics. k> 

Pathology, Histology,. . n 

Pharmacy, . . . .12 

Physical Diagnosis, . . 11 

Physiology, . . . .11 

Practice of Medicine, . 11, 12 

Prescription Books, . . 12 

PQuiz-Compends ? . 14,15 
Skin Diseases, . . .12 

Surgery and Bandaging, . 13 
Therapeutics, . . 

Urine and Urinary Organs, 13 
Venereal Diseases, . .13 


PUBLISHED BY 

P. BLAKISTON, SON & CO., 

Medical Booksellers> Importers and Publishers. 

LARGE STOCK OF ALL STUDENTS* BOOKS, AT 
THE LOWEST PRICES. 

1012 Walnut Street, Philadelphia. 


*** For sale by all Booksellers, or any book will be sent by mail^ 
postpaid, upon receipt of price. Catalogues of books on all branches 
of Medicine, Dentistry, Pharmacy, etc., supplied upon application. 


GOULD’S ) o 
DICTIONARY J See Page l6. 














“An excellent Series of Manuals .”—Archives of Gynaecology. 

A NEW SERIES OF 

STUDENTS’ MANUALS 


On the various Branches of Medicine and Surgery. 

Can be used by Students of any College. 

Price of each, Handsome Cloth, $3.00. Full Leather, $3.50 

The object of this series is to furnish good manuals 
for the medical student, that will strike the medium 
between the compend on one hand and the prolix text¬ 
book on the other—to contain all that is necessary for 
the student, without embarrassing him with a flood of 
theory and involved statements. They have been pre¬ 
pared by well-known men, who have had large experience 
as teachers and writers, and who are, therefore, well 
informed as to the needs of the student. 

Their mechanical execution is of the best—good type 
and paper, handsomely illustrated whenever illustrations 
are of use, and strongly bound in uniform style. 

Each book is sold separately at a* remarkably low 
price, and the immediate success of several of the 
volumes shows that the series has met with popular 
favor. 


No. 1. SURGERY. 318 Illustrations. 

Third Edition. 

A Manual of the Practice of Surgery. By Wm. J. 

Walsham, m.d., Asst. Surg. to, and Demonstrator of 

Surg. in, St. Bartholomew’s Hospital, London, etc. 

318 Illustrations. 

Presents the introductory facts in Surgery in clear, precise 
language, and contains all the latest advances in Pathology, 
Antiseptics, etc. 

“ It aims to occupy a position midway between the pretentious 
manual and the cumbersome System of Surgery, and its general 
character may be summed up in one word—practical .”—The Medi¬ 
cal Bulletin. 

“ Walsham, besides being an excellent surgeon, is a teacher in 
its best sense, and having had very great experience in the 
preparation of candidates for examination, and their subsequent 
professional career, may be relied upon to have carried out his 
work successfully. Without following out in detail his arrange¬ 
ment, which is excellent, we can at once say that his book is an 
embodiment of modern ideas neatly strung together, with an amount 
of careful organization well suited to the candidate, and, indeed, to 
Mi.- practitioner .”—British Medical Journal. 

Price of each Book, Cloth, $3.00; Leather, $3.50. 


THE NEW SERIES OF MANUALS. 


3 


No. 2. DISEASES OF WOMEN. 150 Illus. 

NEW EDITION. 

The Diseases of Women. Including Diseases of the 
Bladder and Urethra. By Dr. F. Winckel, Professor 
of Gynaecology and Director of the Royal University 
Clinic for Women, in Munich. Second Edition. Re¬ 
vised and Edited by Theophilus Parvin, M.D., 
Professor of Obstetrics and Diseases of Women and 
Children in Jefferson Medical College. 150 Engrav¬ 
ings, most of which are original. 

“ The book will be a valuable one to physicians, and a safe and 
satisfactory one to put into the hands of students. It is issued in a 
neat and attractive form, and at a very reasonable price.”— Boston 
Medical and Surgical Journal. 

No. 3. OBSTETRICS. 227 Illustrations. 

A Manual of Midwifery. By Alfred Lewis Gala*bin, 
M.A., M.D., Obstetric Physician and Lecturer on Mid¬ 
wifery and the Diseases of Women at Guy’s Hospital, 
London; Examiner in Midwifery to the Conjoint 
Examining Board of England, etc. With 227 Illus. 

“ This manual is one we can strongly recommend to all who 
desire to study the science as well as the practice of midwifery. 
Students at the present time not only are expected to know the 
principles of diagnosis, and the. treatment of the various emergen¬ 
cies and complications that occur in the practice of midwifery, but 
find that the tendency is for examiners to ask more questions 
relating to the science of the subject than was the custom a few 
years ago. * * * The general standard of the manual is high; 
and wherever the science and practice of midwifery are well taught 
it will be regarded as one of the most important text-books on the 
subject.”— London Practitioner. 

No. 4. PHYSIOLOGY. Sixth Edition. 

254 ILLUSTRATIONS AND A GLOSSARY. 

A Manual of Physiology. By Gerald F. Yeo, m.d., 
f.r.C S., Professor of Physiology in King’s College, 
London. 254 Illustrations and a Glossary of Terms. 
Sixth American from last English Edition, revised and 
improved. 

This volume was specially prepared to furnish students with a 
new text-book of Physiology, elementary so far as to avoid theories 
which have not borne the test of time and such details of methods 
as are unnecessary for students in our medical colleges. 

“ The brief examination I have given it was so favorable that I 
placed it in the list of text-books recommended in the circular of the 
University Medical College.” — Prof. Lewis A. Sthnson, m.d., 
37 East 33d Street, New York. 

Price of each Book, Cloth, $3.00; Leather, $3.50. 



4 


THE NEW SERIES OF MANUALS. 


No. 5. DISEASES OF CHILDREN. 

SECOND EDITION. 

A Manual. By J. F. Goodhart, m.d., Phys. to the 
Evelina Hospital for Children; Asst. Phys. to 
Guy’s Hospital, London. Second American Edition. 
Edited and Rearranged by Louis Starr, m.d., Clinical 
Prof, of Dis. of Children in the Hospital of the Univ. 
of Pennsylvania, and Physician to the Children’s Hos¬ 
pital, Phila. Containing many new Prescriptions, a list 
of over 50 Formulae, conforming to the U. S. Pharma¬ 
copoeia, and Directions for making Artificial Human 
Milk, for the Artificial Digestion of Milk, etc. Illus. 

“ The author has avoided the not uncommon error of writing a 
book on general medicine and labeling it * Diseases of Children,’ 
but has steadily kept in view the diseases which seemed to be 
incidental to childhood, or such points in disease as appear to be so 
peculiar to or pronounced in children as to justify insistence upon 
them. * * * A safe and reliable guide, and in many ways 
admirably adapted to the wants of the student and practitioner.”— 
American Journal of Medical Science. 

No. 6. MATERIA MEDIC A, PHARMACY, 
PHARMACOLOGY, AND THE¬ 
RAPEUTICS. 

JUST READY. 

A Handbook for Students. By Wm. Hale White, 
M.d., F.R.C.P., etc., Physician to, and Lecturer on Ma¬ 
teria Medica, Guy’s Hospital; Examiner in Materia 
Medica, Royal College of Physicians, London, etc. 
American Edition. Revised by Reynold W. Wilcox, 
m.a., m.d., Prof, of Clinical Medicine at the New York 
Post-Graduate Medical School and Hospital; Assistant 
Visiting Physician Bellevue Hospital. 580 pages. 

In preparing this book, the wants of the medical student of to-day 
have been constantly kept in view. The division into several sub¬ 
jects, which are all arranged in a systematic, practical manner, will 
be found of great help in mastering the whole. The work of the 
editor has been mainly in the line of adapting the book to the use 
of American students; at the same time, however, he has added 
much new material. Dr. Wilcox's long experience in teaching 
and writing on therapeutical subjects particularly fits him for the 
position of editor, and the double authorship has resulted in mak¬ 
ing a very complete handbook, containing much minor useful in¬ 
formation that if prepared by one man might have been overlooked. 

Price of each Book, Cloth, $3.00 ; Leather, $3.50. 



THE NEW SERIES OF MANUALS. 


5 


No. 7. MEDICAL JURISPRUDENCE AND 
TOXICOLOGY. 

THIRD REVISED EDITION. 

By John J. Reese, m.d., Professor of Medical Jurispru¬ 
dence and Toxicology in the University of Pennsyl¬ 
vania ; President of the Medical Jurisprudence Society 
of Phila.; Third Edition, Revised and Enlarged. 

“This admirable text-book."— Atner.Jour. of Med. Sciences. 
“We lay this volume aside, after a careful perusal of its pages, 
with the profound impression that it should be in the hands of every 

doctor and lawyer. It fully meets the wants of all students. 

He has succeeded in admirably condensing into a handy volume all 
the essential points."— Cincinnati Lancet and Clinic. 

No. 8. DISEASES OP THE EYE. 176 Illus. 

FOURTH EDITION. JUST READY. 

Diseases of the Eye and their Treatment. A Handbook 
for Physicians and Students. By Henry *R. Swanzy, 
A.m., M.B., f. R.c.s.i., Surgeon to the National Eye and 
Ear Infirmary; Ophthalmic Surgeon to the Adelaide 
Hospital, Dublin; Examiner in Ophthalmic Surgery 
in the Royal University of Ireland. Fourth Edition, 
Thoroughly Revised. 176 Illustrations and a Zephyr 
Test Plate. 500 pages. 

“ Mr. Swanzy has succeeded in producing the most intellectually 
conceived and thoroughly executed resumi of the science within 
the limits he has assigned himself. As a ‘students' handbook,' 
small in size and moderate in price, it can hardly be equaled."— 
Medical News. 

“ A full, clear, and comprehensive statement of Eye Diseases 
and their treatment, practical and thorough, and we feel fully jus¬ 
tified in commending it to our readers. It is written in a clear and 
forcible style, presenting in a condensed yet comprehensive form 
current and modern information that will prove alike beneficial to 
the student and general practitioner.”— Southern Practitioner. 

No. 9. MENTAL DISEASES. 

WITH ILLUSTRATIONS. JUST READY. 
Lectures on Mental Diseases, designed for Medical Stu¬ 
dents and General Practitioners. By Henry Putnam 
Stearns, a.m., m.d., Physician Superintendent at the 
Hartford Retreat, Lecturer on Mental Diseases in Yale 
University, New Haven, Conn., Hon. Mem. British 
Psycho. Asso’n, etc. With Illustrations and a Digest of 
the Laws of the various States relating to the Commit¬ 
ment and Care of the Insane. 636 pages. 

Price of each Book, Cloth, $3.00; Leather, $3.50. 




6 


STUDENTS’ TEXT-BOOKS AND MANUALS. 


ANATOMY. 

Morris’ New Text-Book on Anatomy. Now Rtady. By 
ten leading Surgeons and Anatomists, and Edited by Henry 
Morris, f.r.c.s. 791 Specially Engraved Illustrations, 214 of 
which are printed in colors. Octavo. 1280 pages. 

Price in Cloth, 7.50; Sheep, 8.50 ; Half Russia, 9.50. 
*** Send for Descriptive Circular and Sample Pages. 

Macalister's Human Anatomy. 8x6 Illustrations. A new 
Text-book for Students and Practitioners, Systematic and Topo¬ 
graphical, including the Embryology, Histology, and Morphology 
of Man. With special reference to the requirements of 
Practical Surgery and Medicine. With 816 Illustrations, 
400 of which are original. Octavo. Cloth, 7.50; Leather, 8.50 

Ballou’s Veterinary Anatomy and Physiology. Illustrated. 
By Wm. R. Ballou, m.d., Professor of Equine Anatomy at New 
York College of Veterinary Surgeons. 29 graphic Illustrations. 
i2mo. Cloth, 1.00; Interleaved for notes, 1.25 

Holden’s Dissector. A manual of Dissection of the Human 
Body. Sixth Edition. Edited by A. Hewson, m.d.. Demonstra¬ 
tor of Anatomy at Jefferson Medical College. Over 300 Illus¬ 
trations, many of which are new. Octavo. Nearly Ready. 

Holden’s Human Osteology. Comprising a Description of the 
Bones, with Colored Delineations of the Attachments of the 
Muscles. The General and Microscopical Structure of Bone and 
its Development. With Lithographic Plates and Numerous Illus¬ 
trations. Seventh Edition. 8vo. Cloth, 6.00 

Holden’s Landmarks, Medical and Surgical. 4th Ed. Clo.,1.25 

Potter’s Compend of Anatomy. Fifth Edition. Enlarged. 
16 Lithographic Plates. 117 Illustrations. See page 14. 

Cloth, 1.00; Interleaved for Notes, 1.25 

CHEMISTRY. 

Bartley’s Medical Chemistry. Third Edition. A text-book 
prepared specially for Medical, Pharmaceutical, and Dental Stu¬ 
dents. With 50 Illustrations, Plate of Absorption Spectra and 
Glossary of Chemical Terms. Revised and Enlarged. Cloth,- 

Trimble. Practical and Analytical Chemistry. A Course in 
Chemical Analysis, by Henry Trimble, Prof, of Analytical Chem¬ 
istry in the Phila. College of Pharmacy. Illustrated. Fourth 
Edition, Enlarged. 8vo. Cloth, 1.50 

Bloxam’s Chemistry, Inorganic and Organic, with Experiments. 
Seventh Edition. 281 Illustrations. Cloth, 4.50; Leather, 5.50 
See pages 2 to j for list of Students' Manuals. 





STUDENTS' TEXT-BOOKS AND MANUALS. 


7 


Chemistry : — Continued. 

Richter’s Inorganic Chemistry. Fourth American, from Sixth 
German Edition. Translated by Prof. Edgar F. Smith, ph.d. 
89 Wood Engravings and Colored Plate of Spectra. Cloth, 2.00 
Richter’s Organic Chemistry, or Chemistry of the Carbon 
Compounds. Illustrated. Second Edition. Cloth, 4.50 

Symonds. Manual of Chemistry, for the special use of Medi¬ 
cal Students. By Brandrkth Symonds, a.m., m.d., Asst. 
Physician Roosevelt Hospital, Out-Patient Department; Attend¬ 
ing Physician Northwestern Dispensary, New York. Cloth, 2.00 
Leffmann’s Compend of Chemistry. Inorganic and Organic. 
Including Urinary Analysis. Third Edition. Revised. 

See page 15. Cloth, 1.00; Interleaved for Notes, 1.25 

Leffmann and Beam. Progressive Exercises in Practical 
Chemistry. i2mo. Illustrated. Cloth, 1.00 

Muter. Practical and Analytical Chemistry. Fourth Edi¬ 
tion. Revised, to meet the requirements of American Medical 
Colleges, by Prof. C. C. Hamilton. Illustrated. Cloth, 1.25 
Holland. The Urine, Common Poisons, and Milk Analysis, 
Chemical and Microscopical. For Laboratory Use. Fourth 
Edition, Enlarged. Illustrated. Cloth, 1.00 

Van Niiys. Urine Analysis. Illus. Cloth, 2.00 

CHILDREN. 

Goodhart and Starr. The Diseases of Children. Second 
Edition. By J. F. Goodhart, m.d., Physician to the Evelina 
Hospital for Children; Assistant Physician to Guy’s Hospital, 
London. Revised and Edited by Louis Starr, m.d., Clinical 
Professor of Diseases of Children in the Hospital of the Univer¬ 
sity of Pennsylvania; Physician to the Children’s Hospital, 
Philadelphia. Containing many Prescriptions and Formulae, 
conforming to the U. S. Pharmacopoeia, Directions for making 
Artificial Human Milk, for the Artificial Digestion of Milk, etc. 
Illustrated. Cloth, 3.00; Leather, 3.50 

Hatfield. Diseases of Children. By M. P. Hatfield, m.d.. 
Professor of Diseases of Children, Chicago Medical College. 
Colored Plate. i2mo. Cloth, 1.00; Interleaved, 1.25 

Starr. Diseases of the Digestive Organs in Infancy and 
Childhood. With chapters on the Investigation of Disease, 
and on the General Management of Children. By Louis Starr, 
m.d.. Clinical Professor of Diseases of Children in the Univer¬ 
sity of Pennsylvania. Illus. Second Edition. Cloth, 2.25 

See Pages 14 and 15 for list 0/? Quiz-Comp ends f 



3 


STUDENTS' TEXT-BOOKS AND MANUALS. 


DENTISTRY. 

Fillebrown. Operative Dentistry. 330 Illus. Cloth, 2.50 
Flagg’s Plastics and Plastic Filling. 4th Ed. Cloth, 4.00 

Gorgas. Dental Medicine. Fourth Edition. Cloth, 3.50 

Harris. Principles and Practice of Dentistry. Including 
Anatomy, Physiology, Pathology, Therapeutics, Dental Surgery 
and Mechanism. Twelfth Edition. Revised and enlarged by 
Professor Gorgas. 1028 Illustrations. Cloth, 7.00 ; Leather, 8.00 
Richardson’s Mechanical Dentistry. Sixth Edition. By 
Warren. 6co Illustrations. 8vo. Cloth, 4.50; Leather, 5.50 
Sewill. Dental Surgery. 200 Illustrations. 3d Ed. Clo., 3.00 
Taft’s Operative Dentistry. Dental Students and Practitioners. 

Fourth Edition. 100 Illustrations. Cloth, 4.25 ; Leather, 5.00 
Talbot. Irregularities of the Teeth, and their Treatment. 

Illustrated. 8vo. Second Edition. Cloth, 3.00 

Tomes’ Dental Anatomy. Third Ed. 191 Illus. Cloth, 4.00 
Tomes’ Dental Surgery. 3d Edition. 292 Illus. Cloth, 5.00 
Warren. Compend of Dental Pathology and Dental Medi¬ 
cine. Illustrated. 2d Ed. Cloth, 1.00; Interleaved, 1.25 

DICTIONARIES. 

Gould’s New Medical Dictionary. Containing the Definition 
and Pronunciation of all words in Medicine, with many useful 
Tables etc. Dark Leather, 3.25 ; Mor., Thumb Index, 4.25 
Gould’s Pocket Dictionary. 12,000 Medical Words Pro¬ 
nounced and Defined. Containing many Tables and an 
Elaborate Dose List. Thin 64mo. 

Leather, gilt edges, 1.00; with Thumb Index, 1.25 

Harris’ Dictionary of Dentistry. Fifth Edition. Completely 
revised by Prof. Gorgas. Cloth, 5.00; Leather, 6.00 

Cleaveland’s Pronouncing Pocket Medical Lexicon. Small 
pocket size. Cloth, red edges .75 , pocket-book style, 1.00 

Longley’s Pocket Dictionary. The Student's Medical Lexicon, 
giving Definition and Pronunciation, with an Appendix giving 
Abbreviations used in Prescriptions, Metric Scale of Doses, etc. 
24010. Cloth, 1.00; pocket-book style, 1.25 

EYE. 

Hartridge on Refraction. 5th Edition. Illus. Cloth, 2.00 

Swanzy. Diseases of the Eye and their Treatment. 176 
Illustrations. Fourth Edition. Cloth, 300; Leather, 3.50 

Fox and Gould. Compend of Diseases of the Eye and 
Refraction. 2d Ed. Enlarged. 71 Illus. 39 Formulae. 

Cloth, 1.00 ; Interleaved for Notes, 1.25 

See pages 2 to 5 for list of Students’ Manuals. 



STUDENTS’ TEXT-BOOKS AND MANUALS. 


9 


ELECTRICITY. 

Bigelow. Plain Talks on Medical Electricity. 
Mason’s Compend of Medical Electricity. 
Steavenson and Jones. Medical Electricity. 
Handbook. Just Ready. Illustrated. i2mo. 


Cloth, i.oo 
Cloth, i.oo 
A Practical 
Cloth, 2.50 


HYGIENE. 

Coplin and Bevan. Practical Hygiene. By W. M. L. Cop- 
lin, Adjunct Professor of Hygiene, Jefferson Medical College, 
Philadelphia, and Dr. D. Bevan. Illustrated. Nearly Ready. 
Parkes’ (Ed. A.) Practical Hygiene. Seventh Edition, en¬ 
larged. Illustrated. 8vo. Cloth, 4.50 

Parkes’ (L. C.) Manual of Hygiene and Public Health. 
Second Edition. 12010. Cloth, 2.50 

Wilson’s Handbook of Hygiene and Sanitary Science. 

Seventh Edition. Revised and Illustrated. Cloth, 3.25 


MATERIA MEDICA AND THERAPEUTICS. 

Potter’s Compend of Materia Medica, Therapeutics, and 
Prescription Writing. Fifth Edition, revised and improved. 
See page 15. Cloth, 1.00; Interleaved for Notes, 1.25 

Davis. Essentials of Materia Medica and Prescription 
Writing. By J. Aubrey Davis, m.d., Demonstrator of Obstet¬ 
rics and Quiz-Master on Materia Medica, University of Penn¬ 
sylvania. i2mo. Interleaved. Net, 1.50 

Biddle’s Materia Medica. Twelfth Edition. By the late 
John B. Biddle, m.d. Revised by Clement Biddle, m.d. 8vo. 
Illustrated. Cloth, 4.25; Leather, 5.00 

Potter. Handbook of Materia Medica, Pharmacy, and 
Therapeutics. Including Action of Medicines, Special Thera¬ 
peutics, Pharmacology, etc. By Sami. O. L. Potter, m.d., 
m.r.c.p. (Lond.), Professor of the Practice of Medicine in 
Cooper Medical College, San Francisco. Fourth Revised and 
Enlarged Edition. 776 pages. 8vo. Cloth, 4.00; Leather, 5.00 

White and Wilcox. Materia Medica, Pharmacy, Phar¬ 
macology, and Therapeutics. A Handbook for Students. 
By Wm. Hale White, m.d., f.r.c.p., etc., Physician to and 
Lecturer on Materia Medica, Guy’s Hospital. Revised by 
Reynold W. Wilcox, m.d., Professor of Clinical Medicine at the 
New York Post Graduate Medical School, Assistant Physician 
Bellevue Hospital, etc. American Edition. Clo., 3.00; Lea., 3.50 
See pages 14 and ij /or list of ? Quiz- Compends ? 



10 STUDENTS’ TEXT-BOOKS AND MANUALS. 


MEDICAL JURISPRUDENCE. 

Reese. A Text-book of Medical Jurisprudence and Toxi¬ 
cology. By John J. Reese, m.d.. Professor of Medical Juris¬ 
prudence and Toxicology in the Medical Department of the 
University of Pennsylvania; Physician to St. Joseph’s Hospital. 
Third Edition. Cloth, 3.00; Leather, 3.50 

NERVOUS DISEASES. 

Gowers. Manual of Diseases of the Nervous System. 

A Complete Text-book. By William R. Gowers, m.d.. Prof. 
Clinical Medicine, University College, London. Physician to 
National Hospital for the Paralyzed and Epileptic. Second 
Edition. Revised, Enlarged, and in many parts Rewritten. 
With many new Illustrations. Octavo. 

Vol. I. Diseases of the Nerves and Spinal Cord. 616 
pages. Cloth, 3.50 

Vol. II. Diseases of the Brain and Cranial Nerves. 
General and Functional Diseases. Cloth, 4.50 

Ormerod. Diseases of Nervous System, Student's Guide to. 
By J. A. Ormerod, m.d., Oxon., f.r.c.p. (London), Member Path¬ 
ological, Clinical, Ophthalmological, and Neurological Societies, 
Physician to National Hospital for Paralyzed and Epileptic and 
to City of London Hospital for Diseases of the Chest, Demon¬ 
strator of Morbid Anatomy, St. Bartholomew’s Hospital, etc. 

With 75 Wood Engravings. Cloth, 2.00 

OBSTETRICS AND GYNAECOLOGY. 

Davis. A Manual of Obstetrics. By Edw. P. Davis, Clinical 
Lecturer on Obstetrics, Jefferson Medical College, Philadelphia. 
Colored Plates, and 130 other Illustrations. i2mo. Cloth, 2.00 

Byford. Diseases of Women. The Practice of Medicine and 
Surgery, as applied to the Diseases and Accidents Incident to 
Women. By W. H. Byford, a.m., m.d., Professor of Gynaecology 
in Rush Medical College and of Obstetrics in the Woman's Med¬ 
ical College, etc., and Henry T. Byford, m.d.. Surgeon to the 
Woman's Hospital of Chicago. Fourth Edition. Revised and 
Enlarged. 306 Illustrations, over 100 of which are original. 
Octavo. 832 pages. Cloth, 5.00; Leather, 6.00 

Lewers’ Diseases of Women. A Practical Text-book. 139 
Illustrations. Second Edition. Cloth, 2.50 

Parvin’s Winckel’s Diseases of Women. Second Edition. 
Including a Section on Diseases of the Bladder and Urethra. 
150 Illus. Revised. See page 3. Cloth, 3.00; Leather, 3.50 

Wells. Compend of Gynaecology. Illustrated. Cloth, 1.00 

Winckel’s Obstetrics. A Text-book on Midwifery, includ¬ 
ing the Diseases of Childbed. By Dr. F. Winckel, Professor 
of Gynaecology, and Director of the Royal University Clinic for 
Women, in Munich. Authorized Translation, by J Clifton 
Edgar, m.d., Lecturer on Obstetrics, University Medical Col¬ 
lege, New York, with nearly 200 handsome Illustrations, the 
majority of which are original. 8vo. Cloth, 6.00 ; Leather, 7.00 

4 ®"* See Pages 2 to 3 for list of New Manuals. 



STUDENTS' TEXT-BOOKS AND MANUALS. 


11 


Obstetrics and Gyncecology : — Continued. 

Landis’ Compend of Obstetrics. Illustrated. 5th Edition, 
Enlarged. By Wells. Cloth, 1.00; Interleaved for Notes, 1.25 

Oalabin’s Midwifery. By A. Lewis Galabin, m.d., f.r.c.f. 
227 Illustrations. Leather, 3.50 

PATHOLOGY, HISTOLOGY, ETC. 

Stirling. Outlines of Practical Histology. A Manual for 
Students. 2d Edition. 368 Illustrations. i2mo. Cloth, 3.00 
Wethered. Medical Microscopy. By Frank J. Wethered. 
M.D., m.r.c.p. 98 Illustrations. Cloth, 2.50 

Bowlby. Surgical Pathology and Morbid Anatomy, for 
Students. 135 Illustrations. i2mo. Cloth, 2.00 

Gilliam’s Essentials of Pathology. A Handbook for Students. 
47 Illustrations, nmo. Cloth, 2.00 

Virchow’s Post-Mortem Examinations. 3d Ed. Cloth, 1.00 

PHYSICAL DIAGNOSIS. 

Fenwick. Student’s Guide to Physical Diagnosis. 7th 
Edition. 117 Illustrations, nmo. Cloth, 2.25 

Tyson’s Student’s Handbook of Physical Diagnosis. Illus¬ 
trated. 2d Edition, nmo. Cloth, 1.50 

PHYSIOLOGY. 

Yeo’s Physiology. Sixth Edition. The most Popular Stu¬ 
dents' Book. By Gerald F. Yeo, m.d., f.r.c.s., Professor of 
Physiology in King’s College, London. Small Octavo. 254 
carefully printed Illustrations. With a Full Glossary and Index. 
See page 3. Cloth, 3.00; Leather, 3.50 

Brubaker’s Compend of Physiology. Illustrated. Seventh 
Edition. Cloth, 1.00 ; Interleaved for Notes, 1.25 

Kirke’s Physiology. New 13th Ed. Thoroughly Revised and 
Enlarged. 502 Illustrations, some of which are printed in colors. 
( Blakiston's Authorized Edition .) Red Cl., 4.00; Leather, 5.00 
Landois’ Human Physiology. Including Histology and Micro¬ 
scopical Anatomy, and with special reference to Practical Medi¬ 
cine. Fourth Edition. Translated and Edited by Prof. Stirling. 
845 Illustrations. Cloth, 7.00; Leather, 8.00 

“ With this Text-book at his command, no student could fail in 
his examination.”— Lancet. 

Sanderson’s Physiological Laboratory. Being Practical Ex¬ 
ercises for the Student. 350 Illustrations. 8vo. Cloth, 5.00 

PRACTICE. 

Taylor. Practice of Medicine. A Manual. By Frederick 
Taylor, m.d., Physician to, and Lecturer on Medicine at, Guy’s 
Hospital, London ; Physician to Evelina Hospital for Sick Chil¬ 
dren, and Examiner in Materia Medica and Pharmaceutical 
Chemistry, University of London. Cloth, 2.00; Leather, 2.50 

See pages 14 and 13 for list 0/ ? Quiz-Compends / 



12 STUDENTS' TEXT-BOOKS AND MANUALS. 


Practice :— Continued. 

Roberts’ Practice. New Revised Edition. A Handbook 
of the Theory and Practice of Medicine. By Frederick T. 
Roberts, m.d., m.r.c.p.. Professor of Clinical Medicine and 
Therapeutics in University College Hospital, London. Seventh 
Edition. Octavo. Cloth, 5.50; Sheep, 6.50 

Hughes. Compend of the Practice of Medicine. 4th Edi¬ 
tion. Two parts, each, Cloth, 1.00; Interleaved for Notes, 1.25 
Part i.— Continued, Eruptive and Periodical Fevers, Diseases 
of the Stomach, Intestines, Peritoneum, Biliary Passages, Liver, 
Kidneys, etc., and General Diseases, etc. 

Part ii. —Diseases of the Respiratory System, Circulatory 
System, and Nervous System; Diseases of the Blood, etc. 
Physicians’ Edition. Fourth Edition. Including a Section 
on Skin Diseases. With Index. 1 vol. Full Morocco, Gilt, 2.50 
From John A. Robinson , M.D., Assistant to Chair 0/ Clinical 
Medicine,nowLecturer on Materia Medica, Rush Medical Col¬ 
lege, Chicago. 

“ Meets with my hearty approbation as a substitute for the 
ordinary note books almost universally used by medical students. 
It is concise, accurate, well arranged, and lucid, . . . just the 

thing for students to use while studying physical diagnosis and the 
more practical departments of medicine." 

PRESCRIPTION BOOKS. 

Wythe’s Dose and Symptom Book. C&mtaining the Doses 
and Uses of all the principal Articles of the Materia Medica, etc. 
Seventeenth Edition. Completely Revised and Rewritten. Just 
Ready. 32010. Cloth, 1.00; Pocket-book style, 1.25 

Pereira’s Physician’s Prescription Book. Containing Lists 
of Terms, Phrases, Contractions, and Abbreviations used in 
Prescriptions, Explanatory Notes, Grammatical Construction of 
Prescriptions, etc., etc. By Professor Jonathan Pereira, m.d. 
Sixteenth Edition. 32010. Cloth, 1.00; Pocket-book style, 1.25 

PHARMACY. 

Stewart’s Compend of Pharmacy. Based upon Remington's 
Text-book of Pharmacy. Fourth Edition, Revised. With new 
Tables, Index, Etc. Cloth, 1.00 ; Interleaved for Notes, 1.25 

Robinson. Latin Grammar of Pharmacy and Medicine. 

By H. D. Robinson, ph.d.. Professor of Latin Language and 
Literature, University of Kansas, Lawrence. With an Intro¬ 
duction by L. E. Sayre, ph.g.. Professor of Pharmacy in, and 
Dean of, the Dept, of Pharmacy, University of Kansas, umo. 
Second Edition. Cloth,2.oo 

SKIN DISEASES. 

Crocker. Diseases of the Skin, their Description, Pathology, 
Diagnosis, and Treatment, with Special Reference to the Skin 
Eruptions of Children. By H. Radcliffe Crocker, f.r.c p., Phy¬ 
sician for Diseases of the Skin in University College Hospital. 
Second Edition. Revised and Enlarged, with 92 Wood-cuts. 

Cloth, 5.00 

Van Harlingen on Skin Diseases. A Handbook of the Dis¬ 
eases of the Skin. By Arthur Van Harlingen, m.d. 3d Edition. 
Enlarged and Illustrated. i2mo. In Press. 

4 ®“ See pages 2 to 5 for list of New Manuals. 



STUDENTS' TEXT-BOOKS AND MANUALS. IS 


SURGERY AND BANDAGING. 

Moullin's Surgery, by Hamilton. 600 Illustrations (some 
colored), 200 of which are original. Second Edition. 

Cloth, net, 7.00; Leather, net, 8.00; Half Russia, net, 9.00 

*** Complete circulars, with sample pages and Illustrations, free 
upon application. 

Jacobson. Operations in Surgery. A Systematic Handbook 
for Physicians, Students, and Hospital Surgeons. By W. H. A. 
Jacobson, b.a. Oxon., f.r.c.s. Eng.; Ass’t Surgeon Guy’s Hos¬ 
pital ; Surgeon at Royal Hospital for Children and Women, etc. 
199 Illustrations. 1006 pages. 8vo. Cloth. 5.00; Leather, 6.00 

Heath’s Minor Surgery, and Bandaging. Tenth Edition. 142 
Illustrations. 60 Formulae and Diet Lists. In Press. 

Horwitz’s Compend of Surgery, Minor Surgery and 
Bandaging, Amputations, Fractures, Dislocations, Surgical 
Diseases, and the Latest Antiseptic Rules, etc., with Differential 
Diagnosis and Treatment. By Orville Horwitz, b.s., m.d.. 
Demonstrator of Surgery, Jefferson Medical College. 5th Edition. 
Enlarged and Rearranged. Many new Illustrations and Formulae. 
i2mo. Cloth, 1.00; Interleaved for the addition of Notes, 1.25 
*** The new Section on Bandaging and Surgical Dressings con¬ 
sists of 32 Pages and 41 Illustrations. Every Bandage of any 
importance is figured. This, with the Section on Ligation of 
Arteries, forms an ample Text-book for the Surgical Laboratory. 
Walsham. Manual of Practical Surgery. Third Edition. 
By Wm. J. Walsham, m.d., f.r.c.s.. Asst. Surg. to, and Dem- 
of Practical Surg. in, St. Bartholomew’s Hospital; Surgeon to 
Metropolitan Free Hospital, London. With 318 Engravings. 
See page 2. Cloth, 3.00; Leather, 3.50 

URINE, URINARY ORGANS, ETC. 

Holland. The Urine, and Common Poisons and The 
Milk. Chemical and Microscopical, for Laboratory Use. Illus¬ 
trated. Fourth Edition. i2mo. Interleaved. Cloth, 1.00 

Ralfe. Kidney Diseases and Urinary Derangements. 42 Illus¬ 
trations. i2mo. 572 pages. Cloth, 2.75 

Marshall and Smith. On the Urine. The Chemical Analysis ot 
the Urine. Colored Plates. i2mo. Cloth, 1.00 

Memminger. Diagnosis by the Urine. Ulus. Cloth, 1.00 
Tyson. On the Urine. A Practical Guide to the Examination 
of Urine. With Colored Plates and Wood Engravings. Eighth 
Edition, Enlarged. i2mo. Cloth, 1.50 

Van Niiys, Urine Analysis. Illus. Cloth, 2.00 

VENEREAL DISEASES. 

Hill and Cooper. Student’s Manual of Venereal Diseases, 
with Formulae. Fourth Edition. i2mo. Cloth, 1.00 


See pages 14 and 15 for list 0/ f Quiz-Comp ends f 



PQUIZ-COMPENDS? 

The Best Compends for Students’ Use 
in the Quiz Class, and when Pre¬ 
paring for Examinations. 

Compiled in accordance with the latest teachings of promi¬ 
nent Lecturers and the most popular Text-books. 

They form a most complete, practical, and exhaustive 
set of manuals, containing information nowhere else col¬ 
lected in such a condensed, practical shape. Thoroughly 
up to the times in every respect, containing many new 
prescriptions and formulae, and over two hundred and 
fifty illustrations, many of which have been drawn and 
engraved specially for this series. The authors have had 
large experience as quiz-masters and attaches of colleges, 
with exceptional opportunities for noting the most recent 
advances and methods. 

Cloth, each $1.00. Interleaved for Notes, $1.25. 

No. 1. HUMAN ANATOMY, " Based upon Gray.” Fifth 
Enlarged Edition, including Visceral Anatomy, formerly 
published separately. 16 Lithograph Plates, New 
Tables, and 117 other Illustrations. By Samuel O. L. 
Potter, m.a., m.d., m.r.c.p. (Lond.), late A. A. Surgeon U. S. 
Army, Professor of Practice, Cooper Medical College, San Fran¬ 
cisco. 

Nos. 2 and 3. PRACTICE OF MEDICINE. Fourth Edi¬ 
tion. By Daniel E. Hughes, m.d., Demonstrator of Clinical 
Medicine in Jefferson Medical College, Philadelphia. In two parts* 
Part I.—Continued, Eruptive, and Periodical Fevers, Diseases 
of the Stomach, Intestines, Peritoneum, Biliary Passages, Liver, 
Kidneys, etc. (including Tests for Urine), General Diseases, etc. 

Part II.—Diseases of the Respiratory System (including Phy¬ 
sical Diagnosis), Circulatory System, and Nervous System; Dis¬ 
eases of the Blood, etc. 

\* These little books can be regarded as a full set of notes upon 
the Practice of Medicine, containing the Synonyms, Definitions, 
Causes, Symptoms, Prognosis, Diagnosis, Treatment, etc., of each 
disease, and including a number of prescriptions hitherto unpub¬ 
lished. 

No. 4. PHYSIOLOGY, including Embryology. Seventh 
Edition. By Albert P. Brubaker, m.d., Prof, of Physiology, 
Penn’a College of Dental Surgery; Demonstrator of Physiology 
in Jefferson Medical College, Philadelphia. Revised, Enlarged, 
with new Illustrations. 

No. 5. OBSTETRICS. Illustrated. Fifth Edition. By 

Henry G. Landis, m.d. Edited by William H. Wells, m.d.. 
Assistant Demonstrator of Clinical Obstetrics, Jefferson College, 
Philadelphia. New Illustrations. 


BLAKISTON'S ? QUIZ-COMPENDS ? 

No. 6. MATERIA MEDICA, THERAPEUTICS, AND 
PRESCRIPTION WRITING. Fifth Revised Edition. 
With especial Reference to the Physiological Action of Drugs, 
and a complete article on Prescription Writing. Based on the 
Last Revision of the U. S. Pharmacopoeia, and including many 
unofficinal remedies. By Samuel O. L. Potter, m.a., m.d., 
m.r.c.p. (Lond.), late A. A. Surg. U. S. Army; Prof, of Practice, 
Cooper Medical College, San Francisco. Improved and Enlarged, 
with Index. 

No. 7. GYNECOLOGY. A Compend of Diseases of Women. 
By Wm. H. Wells, m.d., Ass’t Demonstrator of Obstetrics, 
Jefferson Medical College, Philadelphia. Illustrated. 

No. 8. DISEASES OF THE EYE AND REFRACTION, 

including Treatment and Surgery. By L. Webster Fox, m.d.. 
Chief Clinical Assistant Ophthalmological Dept., Jefferson Med¬ 
ical College, etc., and Geo. M. Gould, m.d. 71 Illustrations, 39 
Formulae. Second Enlarged and Improved Edition. Index. 

No. 9. SURGERY, Minor Surgery and Bandaging. Illus¬ 
trated. Fifth Edition. Including Fractures, Wounds, 
Dislocations, Sprains, Amputations, and other operations; Inflam¬ 
mation, Suppuration, Ulcers, Syphilis, Tumors, Shock, etc. 
Diseases of the Spine, Ear, Bladder, Testicles, Anus, and 
other Surgical Diseases. By Orville Horwitz, a.m., m.d., 
Demonstrator of Surgery, Jefferson Medical College. Revised 
and Enlarged. 98 Formulae and 167 Illustrations. 

No. 10. CHEMISTRY. Inorganic and Organic. For Medical 
and Dental Students. Including Urinary Analysis and Medical 
Chemistry. By Henry Leffmann, m.d., Prof, of Chemistry in 
Penn’a College of Dental Surgery, Phila. Third Edition, Revised 
and Rewritten, with Index. 

No. 11. PHARMACY. Based upon “ Remington’s Text-book 
of Pharmacy.” By F. E. Stewart, m.d., ph.g., Quiz-Master 
at Philadelphia College of Pharmacy. Fourth Edition, Revised. 
No. 12. VETERINARY ANATOMY AND PHYSIOL¬ 
OGY. 29 Illustrations. By Wm. R. Ballou, m.d., Prof, of 
Equine Anatomy at N. Y. College of Veterinary Surgeons. 

No. 13. DENTAL PATHOLOGY AND DENTAL MEDI¬ 
CINE. Containing all the most noteworthy points of interest 
to the Dental student. Second Edition. By Geo. W. Warren, 
d.d.s., Clinical Chief, Penn’a College of Dental Surgery, Phila¬ 
delphia. Second Edition, Enlarged and Illustrated. 

No. 14. DISEASES OF CHILDREN. By Dr. Marcus P. 
Hatfield, Prof, of Diseases of Children, Chicago Medical 
College. Colored Plate. 

Bound in Cloth, $1. Interleaved, for the Addition of Notes, $1.25. 

These books are constantly revised to keep up with 
the latest teachings and discoveries , so that they contain 
all the new methods and principles. No series of books 
are so coitiplete in detail , concise in language, or so well 
printed and bound. Each one forms a complete set of 
notes upon the subject under consideration. 

Illustrated Descriptive Circular Free. 


GOULD’S NEW 

Medical Dictionary. 

Based on Recent Medical Literature. 



Small 8vo, Half Morocco, as above, with Thumb Index, . . $4.25 
Plain Dark Leather, without Thumb Index,.3.25 

A compact, concise Vocabulary, including all 
the Words and Phrases used in medicine, with 
their proper Pronunciation and Definitions. 


“One pleasing feature of the book is that the reader can almost 
invariably find the definition under the word he looks for, without 
being referred from one place to another, as is too commonly the 
case in medical dictionaries. The tables of the bacilli, micrococci, 
leucomai'nes and ptomaines are excellent, and contain a large 
amount of information in a limited space. The anatomical tables 
are also concise and clear. . . . We should unhesitatingly 

recommend this dictionary to our readers, feeling sure that it will 
prove of much value to them .”—American Journal 0/ Medical 
Science. 


JUST PUBLISHED. 

GOULD’S POCKET DICTIONARY. 12,000 
Medical Words Pronounced and Defined. 

Leather, gilt edges, $1.00; with Thumb Index, $1.25 






























Fourth Revised Edition, Potter’s Therapeutics 


A UNIQUE BOOK. 


POTTER’S MATERIA MEDICA, PHARMACY AND THERA¬ 
PEUTICS. Fourth Edition. Revised and Enlarged. A Hand- 
book ; including the Physiological Action of Drugs, Special Therapeutics 
of Diseases, Official and Extemporaneous Pharmacy, etc. By S. O. L. 
Potter, m.a., m.d.. Professor of the Practice of Medicine in Cooper 
Medical College, San Francisco; Late A. A. Surgeon, U. S. Army, etc. 
A new Edition in larger type. Octavo. Cloth, $4.00; Leather, $5.00. 

Dr. Potter has become well known as an able compiler, by his Compends 
of Anatomy, and of Materia Medica, both of which have reached four editions. 
In this book, more elaborate in its design, he has shown his literary abilities to 
much better advantage, and all who examine or use it will agree that he has 
produced a work containing more correct information in a practical, concise 
form than any other publication of the kind. The plan of the work is new, 
and its contents have been combined and arranged in such a way that it offers 
a compact statement of the subject in hand. 

Part I.— Materia Medica and Therapeutics, the drugs being arranged 
in alphabetical order, with the synonym of each first; then the description of 
the plant, its preparations, physiological action, and lastly its Therapeutics. 
This part is preceded by a section on the classification of medicines as follows: 
Agents acting on the Nervous System, Organs of Sense, Respiration, Circu¬ 
lation, Digestive System, on Metabolism (including Restoratives, Alteratives, 
Astringents, Antipyretics, Antiphlogistics and Antiperiodics, etc.). Agents act¬ 
ing upon Excretion, the Generative System, the Cutaneous Surfaces, Microbes 
and Ferments, and upon each other. 

Part II.— Pharmacy and Prescription Writing. Written for the use 
of physicians who put up their own prescriptions. It includes—Weights and 
Measures, English and the Metric Systems. Specific Gravity and Volume. 
Prescriptions.—Their principles and combinations; proper methods of writing 
them; abbreviations used, etc. Stock solutions and preparations, such as a 
doctor should have to compound his own prescriptions. Incompatibility, 
Pharmaceutical and Therapeutical. Liquid, Solid and Gaseous Extempo¬ 
raneous Prescriptions. 

Part III.— Special Therapeutics, an alphabetical List of Diseases—a 
real Index of Diseases —giving the drugs that have been found serviceable 
in each disease, and the authority recommending the use of each; a very im¬ 
portant feature, as it gives an authoritative character to the book that is unusual 
in works on Therapeutics, and displays an immense amount of research on the 
part of the author. 600 prescriptions are given in this part, many being over 
the names of eminent men. 

The Appendix contains lists of Latin words, phrases and abbreviations, with 
their English equivalents, used in medicine, Genitive Case Endings, etc. 36 
Formulae for Hypodermic Injections; a comparison of 10 Formulae of Chloro- 
dyne; Formulae of prominent patent medicines; Poisons and their Antidotes; 
Differential Diagnosis; Notes on Temperature in Disease; Obstetrical Memo¬ 
randa; Clinical Examination of Urine; Medical Ethics; Table of Specific 
Gravities and Volumes; Table showing the number of drops in a fluidrachm 
of various liquids and the weight of one fluidrachm in grains, and a table for 
converting apothecaries’ weights and measures into grams. 





A New Series of Manuals. 

FOR MEDICAL STUDENTS. 

UNIFORM IN SIZE, PRICE AND BINDING. 
Price of Each Book, Cloth, $3.00; Leather, $3.50. 


No. 1. SURGERY. Third Edition. Manual of the Practice of Surgery. 
By Wm. J. Walsham, m.d., Assistant Surgeon to, and Lecturer on Anatomy 
at, St. Bartholomew’s Hospital, London, etc. 318 Illustrations. 

Presents the introductory facts in Surgery in clear, precise language, and contains all the 
latest advances in Pathology, Antiseptics, etc. 

“ It aims to occupy a position midway between the pretentious manual and the cumber¬ 
some System of Surgery, and its general character may be summed up in one word— 
practical."— The Medical Bulletin. 

“ Walsham, besides being an excellent surgeon, is a teacher in its best sense, and having 
had very great experience in the preparation of candidates for examination, and their subse¬ 
quent professional career, may be relied upon to have carried out his work successfully. 
Without following out in detail his arrangement, which is excellent, we can at once say that 
his book is an embodiment of modern ideas neatly strung together, with an amount of careful 
organization well suited to the candidate, and, indeed, to the practitioner."— British Medi¬ 
cal Journal. 

No. 2. DISEASES OF WOMEN. Second Edition. By Dr. F. 

Winckel, Professor of Gynaecology, etc., Royal University of Munich. 
The Translation Edited by Theophilus Parvin, m.d., Professor of 
Obstetrics and Diseases of Women and Children, Jefferson Medical College, 
Philadelphia. 150 Engravings, most o^which are original. 

This work has no superior as a text-book of Diseases of Women in regard to clearness and 
completeness, and in its presentation of the latest scientific knowledge, and of the best prac¬ 
tical rules and methods of treatment. 

" The book will be a valuable one to physicians, and a safe and satisfactory one to put 
into the hands of students. It is issued in a neat and attractive form, and at a very reason¬ 
able price."— Boston Medical and Surgical Journal. 

No. 3. MIDWIFERY. By Alfred Lewis Galabin, m.a., m.d., Obstetric 
Physician to, and Lecturer on Midwifery and the Diseases of Women at, 
Guy’s Hospital, London, etc. 227 fine Engravings. 

“ The illustrations are mostly new and well executed, and we heartily commend this book 
as far superior to any manual upon this subject.”— Archives of Gyneecology, New York. 

“ Sensible, practical and complete.”— Medical Brief. 

“ I have carefully read it over, and, as a teacher of midwifery, I consider the book ought 
to become one of the recognized text-books; the treatment and pathology of the various 
subjects treated are clear and concise.”— y. Algernon Temple, m.d., Prof, of Midwifery, 
and Gyneecology, Trinity Medical School, Toronto. 

No. 4. PHYSIOLOGY. Sixth Edition. By Gerald F. Yeo, m.d., 
f.r.c.S., Professor of Physiology in King’s College, London. Sixth 
American from Second English Edition. 321 carefully printed Illustrations. 

** The work will take a high rank among the smaller text-books of Physiology."— Prof. 
H. P. Bowditch, Harvard Medical School. 

“ By his excellent manual. Prof. Yeo has supplied a want which must have been felt by 
every teacher of Physiology."— The Dublin Journal of Medical Science. 

J®-Sek Next Page. 


P. BLAKISTON, SON & CO., Publishers and Booksellers, 

1012 WALNUT STREET, PHILADELPHIA. 




The New Series of Manuals— Continued. 


No. 5. CHILDREN. Second Edition. Illustrated. By J. F. Good- 
hart, m.d., Physician to the Evelina Hospital for Children; Assistant 
Physician to Guy’s Hospital, London. American Edition. Revised and 
Edited by Louis Starr, m.d., Clinical Professor of Diseases of Children 
in the Hospital of the University of Pennsylvania; Physician to the 
Children’s Hospital of Philadelphia. With Illustrations, 50 Formulae, and 
Directions for preparing Artificial Human Milk, for the Artificial Digestion 
of Milk, etc. 

“ As it is said of some men, so it might be said of some books, that they are ' born to * 
greatness.' This new volume has, we believe, a mission, particularly in the hands of the 
younger members of the profession. In these days of prolixity in medical literature, it is 
refreshing to meet with an author who knows both what to say and when he has said it.”— 
New York Medical Record. 

No. 6. MATERIA MEDICA, PHARMACY, PHARMACOLOGY, 
AND THERAPEUTICS. Just Ready. A Handbook for Students. 
By William Hale White, m.d., f. r.c.p., etc., Physician to, and Lec¬ 
turer on Materia Medica, Guy’s Hospital; Examiner in Materia Medica, 
Royal College of Physicians, London, etc. American Edition. Revised 
by Reynold W. Wilcox, m. a., m. d., Professor of Clinical Medicine at 
the New York Post-Graduate Medical School and Hospital; Assistant 
Visiting Physician Bellevue Hospital. 

" Practical experience with Dr. White’s book on general therapeutics, both as to its use¬ 
fulness to the student and as to the soundness of the advice which he gives, has proved that 
he is an author upon whom much dependence may be placed, and a careful examination of 
the American version of his second work, which has been published under Dr. Wilcox’s 
eye, shows that it is also worthy of both its author and editor.”— Therapeutic Gazette, 
January 16,1893. 

No. 7. MEDICAL JURISPRUDENCE AND TOXICOLOGY. 
Third Edition. By John J. Reese, m.d., Professor of Medical Juris¬ 
prudence and Toxicology, University of Pennsylvania, etc. Third Edition. 
Enlarged. 

“ The production of this admirable text-book by one of the two or three leading teachers 
of medical jurisprudence in America, will, we hope, give a new impetus to the study of 
forensic medicine, which, inviting and important as it is, has heretofore been strangely 
neglected in both legal and medical schools.”— American Journal of the Medical Sciences. 

“ We heartily second the author’s hope that this treatise may encourage an increasing 
interest in the students for that most important, but too much neglected, subject, forensic 
medicine.”— Boston Medical and Surgical Journal. 

No. 8. SWANZY. DISEASES OF THE EYE. Fourth Edition, 
Enlarged and Improved. Diseases of the Eye and their Treatment. 

A Handbook for Physicians and Students. By Henry S. Swanzy, 

A. M., m. b., f. r. c. S. I., Surgeon to the National Eye and Ear Infirmary; 
Ophthalmic Surgeon to the Adelaide Hospital, Dublin; Examiner in Oph¬ 
thalmic Surgery in the Royal University of Ireland. Fourth Edition, 
Thoroughly Revised. 170 Illustrations. 

“ Mr. Swanzy has succeeded in producing the most intellectually conceived and thoroughly 
executed resume of the science within the limits he has assigned himself. As a * students' 
handbook,' small in size and moderate in price, it can hardly be equaled.”— Medical News. 

*** Other Volumes in Preparation. A complete illustrated circular, with 
sample pages, sent free upon application. 

Price of Each Book, Cloth, $3.00; Leather, $3.50. 


P. BLAKISTON, SON & CO., Publishers and Booksellers, 

1012 WALNUT STREET, PHILADELPHIA. 




